Can the positivity bias, observed across various Social Network Sites (SNSs), predict the use of prosocial lies in a SNS such as Facebook? The positivity bias may be a product of politeness norms (i.e., positive face concern) that have influenced communication phenomena before these sites existed. In addition, positive face concern may also be affected by unconscious cues or primes that promote prosocial behavior on Facebook. We conducted an online experiment using current Facebook users to examine how positive face concern and surveillance primes affect prosocial lying in public and private Facebook contexts. Although positive face concern and publicness predicted the use of prosocial lying, positive face concern was not affected by the publicness and surveillance primes did not affect positive face concern or the use of prosocial lies in our study. This hints towards the nuance of positive face concern and the potential limitations of surveillance primes on prosocial lying behavior. (C) 2016 Elsevier Ltd. All rights reserved.