Social media have become a major channel through which consumers interact with firms and other consumers. This paper examines the factors that drive consumers to co-create in social media and proposes a theoretical model that extends the theory of planned behavior to include perceived usefulness as a key antecedent of consumer attitudes toward co-creation in social media. The model was tested using responses from 743 Chinese consumers. Results of structural equation modeling confirmed that perceived usefulness was an antecedent of consumer attitudes toward co-creation in social media. The relationship between perceived usefulness and customer attitudes toward co-creation was moderated by the level of consumer involvement, and that relationship was found to be more salient for a high rather than a low level of consumer involvement. Practical and theoretical implications are given.