QQ is a instant messaging service that are provided by Tencent. According to a news, QQ have over 600 million registered users now.
Recently, Tencent provide a interesting tools that can tell us how many people are online on QQ now.
According to this web site, there are over 161 million users on QQ now (CST 20:53:51, 26th Jun), and the largest number ever is 167 million users.
And we can find that this online user is concentrated at east coastal district and a part of south district. It is same as economically advanced district and areas that have many internet users.
I'm looking forward to when this number will exceed 200 millon :)
Source => QQ official website