Positive beliefs about worry are an important factor that has been shown to be associated with the reduction of worry severity with cognitive behavioural therapy. The present study evaluated the psychometric properties of a measure of positive beliefs about worry, the Why Worry Questionnaire II (WW-II; Hebert et al.,2014, 0.1016/j.paid.2013.08.009) with a clinical sample. The present study also compared mean scores on the WW-II in the present clinical sample with scores found in non-clinical samples. Finally, the study compared mean scores on the WW-II between groups with primary diagnoses of generalized anxiety disorder (GAD), major depressive disorder (MDD) and anxiety disorder not otherwise specified (NOS). The confirmatory factor analysis found the five-factor model an adequate to good fit to the data, and the WW-II demonstrated excellent internal consistency within this clinical sample. Additionally, scores on the WW-II in the present sample were significantly higher than scores found by in their non-clinical sample. Finally, no significant mean differences were found between primary diagnoses of GAD, anxiety disorder NOS or MDD. Important theoretical and clinical implications and suggestions for future research are discussed.