Subjective well-being (SWB) is an important indicator of quality of life. SWB can be conceptualized as a momentary state ( e. g., mood) as well as a relatively stable trait ( e. g., life satisfaction). The validity of self-reported trait aspects of SWB has been questioned by experimental studies showing that SWB judgments seem to be strongly context dependent. Particularly, momentary mood seems to have a strong influence on global SWB judgments. To explore the ecological validity of these conclusions a non-experimental longitudinal self-report study with three occasions of measurement was conducted (N = 249). The associations between momentary mood ratings and global judgments of SWB ( life satisfaction, satisfaction with life domains, frequency and intensity of emotions) as well as personality ratings (self-esteem, optimism, neuroticism, extraversion) were analyzed in a multistate-multitrait-multiconstruct model. This model takes ( a) measurement error, (b) occasion-specific deviations, and ( c) stable interindividual differences into account. It is shown that the variability in global SWB judgments and personality ratings is relatively small and much smaller than the variability in mood. Furthermore, the occasion-specific associations between mood states, on the one hand, and global SWB and personality ratings, on the other hand, are relatively small and inconsistent. All global SWB and personality variables are more strongly related to mood on the trait level than on the occasion-specific deviation level. Therefore, in contrast to experimental studies, occasion-specific mood effects do not seem to be inherently important in ecological measurement settings.