A longstanding hypothesis links affective and behavioral inhibition with cancer incidence and progression though it does not clarify psychometric distinctions among related constructs. We hypothesized that repressive defensiveness, suppression, restraint, and distress would be separable factors in our sample of metastatic breast cancer patients. Our results support the discriminant validity of these constructs in our total sample, and the stability over 1 year in our control group. Using factor analysis, we found 4 separate factors at our prerandomization baseline corresponding closely to hypothesized constructs. Additionally, associations in a multi-trait, multi-occasion (baseline and 1 year) matrix met each of the 3 Campbell and Fiske (1959) criteria of convergent and discriminant validity. Future research testing the links between psychological, physiological, and survival outcomes with affective inhibition in cancer patients will be clearer when informed by these distinctions.