Objective: To psychometrically refine a standardized scale for identifying those lifestyle changes that were most likely to contribute to anxiety and depression among prostate cancer (PCa) patients. Methods: Three hundred and eighty-one PCa patients who had received their initial diagnosis between one and 96 months completed a survey of background variables, anxiety and depression inventories and the 36-item Effects of Prostate Cancer upon Lifestyle Questionnaire (EPCLQ). Results: Levels of anxiety (24%) and depression (26%) were similar to those previously reported for PCa patients. The EPCLQ was shown to have satisfactory psychometric properties and significantly predicted anxiety and depression scores and the presence of psychological clinicity among this sample. Factor analysis of the EPCLQ showed that adverse emotions and social withdrawal, plus loss of cognitive ability, were the most powerful predictors of fear, physiological arousal, discomfort and pain factors underlying anxiety; these factors also predicted pessimism and fatigue factors underlying depression. Conclusions: The EPCLQ was shown to be a reliably sound and valid instrument for assessing important lifestyle changes that predict anxiety and depression among PCa patients. In addition, links between receiving a diagnosis and treatment for PCa and development of psychosocial disturbance via emotional negativity, decreased cognitive performance and withdrawal from others appear to warrant further investigation.