The present study investigated the relationship between perfectionism and depression, and the mediation/moderation effects of optimism. Participants were 126 adults (78% women, mean age = 27 years) who completed an online survey that included the Multidimensional Perfectionism Scale (Frost, Marten, Lahart, & Rosenblate, 1990), the Revised Life Orientation Test (Scheier, Carver, & Bridges, 1994), and the Hamilton Depression Inventory (Reynolds & Kobak, 1995). Maladaptive, adaptive and total perfectionism were examined in separate analyses. In most analyses, the data fit a mediation model. Optimism limited the effect (relationship) of total and maladaptive perfectionism on depression. Adaptive perfectionism was related to depression only through optimism. There was a small gender difference, with indirect effects greater for men. These results are consistent with past research and support the notion that correlations between perfectionism, as a trait, and affective variables must be examined using multivariate models that allow for the determination of complex relationships. (C) 2012 Elsevier Ltd. All rights reserved.