In the present paper, the relationship between illusory superiority (the belief to be better than others) and unrealistic optimism (the expectancy of a better future for oneself than for others) is examined, and the relationship of both self-serving biases to the person positivity bias (the more benign evaluation of individuals as compared to groups) and the self-other asymmetry in social comparison is analysed. High school students rated themselves and a comparison other on a number of characteristics. In addition, they estimated the likelihood of a number of events in their own and the comparison other's future. Both the significant and intercorrelated illusory superiority and unrealistic optimism effects were correlated with locus of control, self-esteem and trait anxiety. Neither phenomenon could be explained by the person positivity hypothesis, and both biases were stronger if the prospects and characteristics of the comparison other were judged firstly than if subjects rated their own attributes firstly. The latter finding offers a replication and an extension of the asymmetry effect in self/other comparisons, and it underlines the strong link between both biases under study.