Determinants of intended condom use with steady and casual sex partners were examined among Dutch HIV-positive men who have sex with men (MSM) (N = 296). Given the proposition that safer sex behavior among HIV-positive people is a form of prosocial behavior, the present study extended the general framework of the Theory of Planned Behavior with Schwartz's norm-activation theory and tested the assumption that personal norms would mediate the effects of other psychosocial factors on intended condom use for anal sex. In addition, it was hypothesized that, depending on the context in which sex occurs, specific motives for unprotected anal sex may have a negative influence on intended condom use and, as such, undermine a prosocial tendency to practice safer sex. Therefore, we also investigated the influence of sexual motives for unprotected anal sex on intended condom use with steady and casual sex partners. Results indicated that the Theory of Planned Behavior adequately predicted condom use intentions (for casual sex partners and steady sex partners, the explained variance was 52% and 53%, respectively). However, our proposed model of sexual decision-making significantly improved the prediction of behavioral intentions. For steady and casual sex partners, the assumption of the mediating role of personal norms on condom use intention was confirmed empirically. Additionally, sexual motives for unprotected anal sex exerted, as expected, a direct, negative effect on condom use intention with casual sex partners. The implications of the findings for future research and the development of HIV-prevention programs for HIV-positive MSM are discussed.