Modern concepts assume that mental health is not just the absence of mental illness but is also characterized by positive well-being. Recent findings indicated a less pronounced distinction of positive and negative mental health dimensions in clinical samples. Self-perceived strengths were associated with markers of mental health in healthy individuals. However, analyses of strengths and their association with different mental health variables in clinical populations are scarce. A cross-sectional design was conducted at a German outpatient training and research center. 274 patients before treatment (female: 66.4%, mean age = 42.53, SD = 13.34, range = 18-79) filled out the Witten Strengths and Resource Form (WIRF), a multidimensional self-report of strengths, as well as other instruments assessing positive and negative mental health variables. Data was analyzed with structural equation modeling and latent regression analyses. Confirmatory factor analysis of the WIRF showed good model fit for the assumed three-subscale solution. Regarding mental health, a one-factor model with positive and negative variables as opposite poles showed acceptable fit. A correlated dual-factor model was not appropriate for the data. All WIRF subscales significantly predicted unique parts of variance of the latent mental illness factor (p = .035 - p < .001). The context-specific assessment of patients' strengths was confirmed and led to an information gain in the prediction of mental health. Results suggest that positive and negative facets of mental health are highly entwined in people with pronounced symptoms. The scientific and practical implications of these findings are discussed.