The paper describes corporate social responsibility (CSR) communication on Facebook and Twitter – how the companies use the social media for accomplishing their CSR communication goals. On the sample of ten global companies with the best CSR reputation research tracks down their social media activity, as well as posts, likes and comments of their customers. Observed companies on average dedicate about 1/10 of their social media communication bandwidth to CSR topics, mainly on Facebook. CSR topics do not seem to be of much interest to the readers (CSR posts are mostly ignored), but at least user sentiment related to CSR messages has been proven to be mostly positive. CSR on social networks is well established, leading CSR companies use this communication channel extensively.