The article deals with the subject of attending online communities by users of different age groups. We analyze a representative sample of Czech population aged 12 years and older, the whole sample consisting of 1.586 respondents, and analyzed replies of 864 Internet users. The research was carried out in September 2007 by using face-to-face interviews. We show that older adolescents aged 16 - 19 years are the most common attendants of virtual groups and that participation decreases with age. Adolescents are also less inhibited in online communities and, if what they claim is true, it seems that virtual groups enrich their lives more than other users. Adolescents have higher needs of meeting people in groups in general and therefore their behavior on the Internet is similar as in real life. The fact that adolescents are less inhibited in these communities could also be caused by them feeling the urge to develop their identities.