Some statistics are available here:
Anatoly Rudenko, president of the Russian Bible Society, in an interview with the editor of the East-West Church & Ministry Report, 6 June 1997, maintained that the number of practicing Christians of all confessions in Russia today is no more than two percent, and probably closer to one percent. If this is the case, Russia has far fewer believers than is generally assumed. In contrast to Rudenko's estimate of 1.7 to 3.3 million practicing Christians, Russian Orthodoxy alone routinely claims 50 to 60 million faithful (33 to 40 percent of the population)....
The disparity between Rudenko's estimate and the dramatically larger figures normally cited may be explained, in large part, by divergent understandings of what constitutes a believer. For example, research by Dimitri Furman reported in Izvestiia revealed that 50 percent of Russians surveyed identified themselves as believers, but less than two percent of these respondents attended church regularly, prayed, or believed in God as a personality. Furthermore, six times more respondents said they attend church regularly than do in reality...
A June 1996 Russian pre-election poll indicated that believers (50 percent of respondents) were far more often nonobservant (37.3 percent) than observant (12.7 percent). And corporate worship was strikingly erratic even among self-described observant believers: 10 percent answered once a week; 13 percent answered once a month; and 55 percent of self-described observant believers answered on religious holidays and on family occasions. Of the 50 percent of respondents who identified themselves as believers, 83 percent considered themselves to be Orthodox (Susan Goodrich Lehmann, "Religious Revival in Russia: Significant or Superficial?," paper presented at the Kennan Institute for Advanced Russian Studies, Washington DC, 21 October 1996).
Interesting anyway.