Objectives Individual differences in stress appraisal, coping, optimism and social support have contributed to variability in adjustment to breast cancer, but less is known about their relative influence particularly at diagnosis. The purpose of this study was to compare the predictive role of these variables on both positive and negative adjustment in a sample of recently diagnosed women. Method Data was collected from 241 women at diagnosis and post-surgery (4?months later). They completed questionnaires which assessed global and cancer-specific stress, general and cancer-specific coping, emotional adjustment (depression, anxiety, positive and negative affect) at Times 1 and 2 and benefit finding at Time 2. Results Hierarchical regression analyses (all p?0.01) taking account of age and cancer related variables (disease stage and type of surgery) showed that stress appraisal was the strongest and most consistent predictor of adjustment. The coping strategies, while significant, were less powerful predictors of emotional adjustment, but they explained more variance than stress on benefit finding. Stress and coping outweighed the impact of social support and optimism. Conclusions Global appraisal of stress was the most powerful predictor in the model, and findings suggest that it contributes to patients' affective status, indicating that women should be screened as part of the diagnostic process to identify those at risk for poor adaptation to the illness. Copyright (c) 2011 John Wiley & Sons, Ltd.