When engineer Zarik Boghossian felt tapped out at his job, he turned to an employment firm to help him find a new one. But after paying $5,000, he says, he got little more than outdated contacts, job leads that were widely available on the Internet, and a 300-page “customized” document with standard career advice.

So when a colleague invited him to join LinkedIn.com, an online social network where professionals can meet peers and make career contacts, he gave it a try. Within a month of joining in April, Mr. Boghossian spotted an intriguing profile – Afshin Behnia, chief executive of Mitratech Inc. He met with this new contact and landed a job as vice president of engineering at the Los Angeles technology and services company.

“Next I want to be a president or chief executive officer of a company,” Mr. Boghossian says. “I think I can get there by [online] networking.”

A growing number of professionals from Los Angeles to Lyon to Lijiang are taking Mr. Boghossian’s path, using online social networks to build up a list of contacts – and potentially land a dream job. Unlike regular employment sites, which mainly list want ads and applicants’ resumes, social networks are designed to be, well, more social.

When job seeking, the idea isn’t necessarily to search for a specific opening – instead, you look for other members who have a common friend or interest. From there, you build a relationship by e-mail and interviews, just as you would in traditional networking.

Fans of the networks claim that the personal connection with other members gets them access to choice jobs that don’t show up in want ads. And, as in the case of Mr. Boghossian, fans say that the networks can put them in touch with top executives, instead of just the human-resource officials they’d reach through an ad.

The online networks “enhance what we’ve always done and empower us to do what we’ve always imagined we could do – if we were naturally great networkers,” said Gerry Crispin, principal at CareerXroads, a recruiting-technology consultant in Kendall Park, N.J.

Professionally oriented social networks have existed for years. But only in the past 18 months have their numbers boomed. Why now? In part, it’s because of the runaway success ofFriendster.com, a network that lets you meet new people through others whom you know in common. Launched in March 2003, Friendster drew millions of members within months. The site’s focus is purely social – but it got people thinking that the Internet could help them improve their professional life as well as their private life.

To be sure, networks are used for a host of business purposes. Many users aren’t even there to find jobs – they simply list themselves to form relationships in their field.

Getting started on professional networking sites such as LinkedIn Ltd.’s LinkedIn, Ryze Ltd.’s Ryze.com, and a site called ZeroDegrees.com by IAC/InterActiveCorp., usually goes like this: A user signs up, creates a password, and fills in a career profile. Many people are invited by friends who already belong, but most sites also let users join on their own. Users can usually choose from a host of privacy features so that, for example, their contact details aren’t visible, or are visible only to people they designate. Some sites are free of charge, others charge fees for certain services (such as contacting other members), and a few are closed except to paying customers.