The aim of this study was to investigate the possibility of predicting anxiety and depression 6 months after the cancer diagnosis on the basis of measures of anxiety, depression (Hospital Anxiety and Depression, HAD scale), subjective distress (Impact of Event, IES scale) and some aspects of social support in connection with the diagnosis. A further purpose was to attempt identification of individual patients at risk of prolonged psychological distress, and to develop an easily applicable clinical tool for such detection. A consecutive population-based series of 522 newly diagnosed patients with breast, colorectal, gastric and prostate cancer were interviewed in connection with the diagnosis and 6 months later. Anxiety and depression close to the diagnosis explained 39% of the variance in anxiety and depression 6 months later. Patients scoring as doubtful cases/cases for HAD anxiety and/or depression were more than 11 times more likely than non-cases to score as doubtful cases/cases at 6 months. Additional risk factors were having an advanced disease and nobody in addition to the family to rely on in case of difficulties. Levels of anxiety and depression at diagnosis predict a similar status 6 months later. The results also indicate that the HAD scale in combination with a single question about social support may be a suitable screening tool for clinical use.