Previous research found that computer-mediated communication (CMC) users affectively compensate for partners when they believe their partners' negative demeanor to be malleable, but unlike in other media, they discount their own influence on their partner. This research examined attributions that chat users make when they influence their partners but do not recognize their own causal influence. Dyads conducted either online text-based conversations or audio interactions. Each male dyad member was told that his female partner (who was actually naive) was in a bad mood or had an unpleasant personality. Although they had rated their ability to influence others' demeanors as lesser when using CMC compared with those who anticipated telephone (audio), males acted more pleasantly when expecting a bad mood, and rated the partner as behaving more pleasantly, in CMC. In CMC, males filled the attributional gap by inferring that partners' behavior reflected partners' liking toward them. These findings extend the hyperpersonal model of CMC to explain how illusions about partners' affection may come to influence the sociability of online interaction and vice versa.