Although a substantial body of research exists on gender differences in Computer Mediated Communication, relatively little empirical attention has been directed toward the special case of CMC - Instant Messenger (IM) and the area of self-disclosure. This study analyzes gender differences and relationships in self-disclosure in the away message of MSN of 329 male and female Taiwanese university students. Applying the five subscales of self-disclosure by Wheeless and Grotz (Wheeless, 1978; Wheeless & Grotz, 1976) and the six topic areas of self-disclosure by Jourard and Lasakow (1958) revealed the following results: Findings show that males and females often do not show the gender differences anymore, which were previously found in face-to-face communication on certain aspects of self-disclosure e.g. frequency, depth, breadth, honesty or accuracy and valence of self-disclosure. However, findings pointing out the different motives and the use of self-disclosure on IM are similar to face-to-face communication, such as females prefer discussing their “personality” while male MSN users prefer “work or studies” especially the more buddies they have. Also males disclose with awareness and intention suggesting the make use of selective self-presentation (Walther, 1996) for rather males than females. Female MSN users write more impulsively in their away message, however they are found to be more selective than males in to whom they chose to disclose or not by blocking buddies. The number of buddies on the buddy list seems to have hardly any effect on males’ and females’ self-disclosure. The gender of buddies on the buddy list as a moderating factor showed that males feel more comfortable (honest and less understated) when disclosing to females. Extra findings include that for both gender self-disclosures on IM is not less honest and not exaggerated, rather understated. Previous findings in face-to-face communication on preferred topics of self-disclosure of both genders of Asian background were confirmed on IM. On IM, self-disclosure by males and females seem to be free of the importance of the degree of social distance within Chinese society as hardly any primary groups and secondary groups but almost only mixed groups of buddies on buddy lists were found.