Fortune magazine also publishes a list of great places to work, the 100 best in America. Winners with headquarters in the Washington area are: Arnold & Porter, Booz Allen Hamilton, Capital One, Marriott, Mitre, Network Appliance, SRA International, and Stanley.

Some of these firms are among The Washingtonian’s Great Places to Work, but some are not. Why do companies show up on one list and not another?

Fortune limits its competition to companies with more than 1,000 workers; The Washingtonian doesn’t. Small and midsize firms compete for our list, too. While small firms may not offer some of the benefits of large ones—such as on-site daycare and gyms—they usually receive higher scores for job satisfaction on employee surveys. The Washingtonian heavily weights employee satisfaction.

Other magazines run lists of best places to work using different criteria. Working Mother, which looks at such things as childcare and maternity leave, named these local firms as winners: Arnold & Porter, Capital One, Covington & Burling, Discovery Communications, Fannie Mae, Inova Health System, and Marriott.

One reason some of these companies aren’t on The Washingtonian’s list: Some didn’t participate in our contest. To limit the number of surveys employees get, some companies don’t participate in every “best places to work” competition—which employees might say makes them a great place to work.