Personality perception accuracy after instant messenger communication and relation of content of messages to self- and stranger-perceived personality were examined in two cultures. Czech and Chinese subjects were paired into couples with a stranger and spoke with him or her through Windows Live Messenger (in the Czech Republic) or QQ (in China). After 30-40 minutes conversation they filled out Big Five questionnaires about their partner’s personality and about themselves. In the Czech study, there was a correlation 0.39 between self-perceived and partner perceived extraversion. In the Chinese study, correlations between self-perception and partner-perception of a subject’s personality were 0.49 for neuroticism, 0.38 for extraversion, 0.35 for openness to experience, and 0.28 for agreeableness. Possible reasons for Chinese higher personality perception accuracy can be higher proneness to “dialectical thinking” or higher experience with using online communication for social sharing and perceiving.