Pretty soon, the only people on Earth without wireless Internet access will be submerged scuba divers, on-the-job coal miners, and my mother. For everyone else, it will be all Internet, all the time.

I'm exaggerating a bit, of course. But according to research firm Gartner, the number of worldwide wireless network hot spots (Wi-Fi access points) will jump from 14,752 in 2002 to 71,079 this year. By 2005, the number should grow to 151,768--which Gartner defines as "critical mass."

Today, though, obtaining wireless Net access can be confusing, cumbersome, and expensive. You have two main options for wireless Internet access away from home: public wireless local-area networks, or WLANs, and wireless wide-area networks, or WWANs. Each has its advantages and disadvantages, depending on what you need--and where you need it.

Trying to decide which wireless path to take? Read on.

WLANs are local-area networks with one or more wireless access points (also known as Wi-Fi hot spots) that enable users to connect without wires. Hot spots are showing up in all sorts of public places today: Starbucks, McDonald's, Borders Book Stores, hotel lobbies and conference rooms, airport departure lounges--even some Manhattan pay phones.

Benefits: WLANs usually offer Internet access that is at least as fast as DSL connections. Most WLAN service providers, such as T-Mobile, offer pay-as-needed plans that don't require month-to-month or annual contracts.

Downsides: You must be within 300 feet of a Wi-Fi hot spot; the further away you are, the weaker the signal--and the slower your speed.

Also, roamers must navigate a patchwork of service providers. For instance, going online at Starbucks requires a T-Mobile account. When you get to the airport, however, you may need a Wayport account. This is what I meant by cumbersome. (You can use the same hardware for each service, however.)

A few municipalities, such as Half Moon Bay, California, have installed "wireless clouds" under which unbroken wireless Internet access is provided. But they are the exception, not the rule.

Other considerations: Most often, mobile professionals jump onto a WLAN using a notebook equipped with 802.11a ,b, or g wireless networking capabilities built in or provided on an adapter. Adapters are available as PC Cards or as USB devices.

PC Card Wi-Fi adapters cost $30 to $120. To compare prices, check the PCWorld.com Product Finder.

Notebooks aren't your only Wi-Fi option, though. Some PDAs, such as the Palm Tungsten C and Toshiba's Pocket PC E755, offer built-in Wi-Fi networking. For a review, read "Pumped-Up PDAs."

You can also add Wi-Fi support, depending upon the PDA. For instance, SanDisk has 802.11b wireless network adapters that fit on Secure Digital and CompactFlash cards. The cards work with Pocket PCs and Palm devices that have those card slots. Expect to pay about $100 for a Wi-Fi card or $150 for a Secure Digital card that combines Wi-Fi networking and storage capacity.

As for access fees, expect to pay anything from zero (for free public Wi-Fi hot spots) to $100 a month or more for unlimited Wi-Fi network access. Rates vary by service provider, length of use, and other factors. For more information, check out my guide to Wi-Fi hot spots and service providers.

WWANs are essentially cellular networks over which subscribers can access the Internet. Not surprisingly, AT&T Wireless, Sprint, Verizon, and other companies also offer wireless Internet service plans.

In the past few years, these companies have been introducing what is sometimes called "3G" (or third-generation) network services for wireless Internet access. In theory, 3G network service should provide Internet access speeds equivalent to DSL or higher. In reality, what most consumers get today is roughly equivalent to a 56K modem. In another year or two, true 3G service is expected to be more readily available in the United States. But for now, "2.5G" is a more accurate term to describe what's being offered.

For more background on 3G networks, see "Mobile Computing: The Newest Wireless Technology" and "Wireless Service Hits DSL Speeds."

Benefits: Unlike the 300-feet limitation of today's Wi-Fi networks, you can go online with a WWAN just about anywhere there's a cell phone signal--the deck of a boat, say, or ballpark bleachers. And depending on your service plan, you can check e-mail from your cell phone, thereby eliminating the need to carry a larger PDA or notebook.

Downsides: Service plans can be confusing. Many providers price usage by kilobytes and megabytes, for instance, whereas Wi-Fi plans are usually priced more logically, by minutes or hours. You may have to sign a one-year service contract, and you may have fewer pricing plans from which to choose. For example, Sprint PCS Vision's service is limited to an $80/month plan for notebook and PDA users. For a look at AT&T Wireless data plan options, see "Mobile Computing: Wireless E-Mail."

Also, to use a notebook with these services, you'll need a pricey modem (usually a PC Card device). Sprint subscribers, for instance, pay $230 to $350 for a Sprint PCS Vision-compatible PC Card modem--that's far more expensive than a Wi-Fi network adapter card.

Ask yourself why you need wireless Net access. Your requirements should help you decide which device you'll need

Ultimately, wireless Net access is freeing, because you can work almost anywhere. But it's also confining, because your clients and your boss can reach you almost anywhere. The trick, as with any technology, is to know when to turn the thing off.