Abstract. The aim of this intensive longitudinal study was to examine the moderating effect of affect on the optimism-health relationship and to separately consider valence and arousal, the basic dimensions of affect. For 14 days 45 students answered three times a day a questionnaire regarding affect and health status. Valence interacts with optimism in the prediction of health and tense arousal moderates the pessimism-health relationship. Findings provide support for the relevance of a two-factor model of dispositional optimism and the importance of separate consideration of the basic affect dimensions in the understanding of the processes between optimism and health.