Distress in cancer patients is common. In the last years, several studies have used the single-item Distress Thermometer (DT) as a screening tool for psychological distress in cancer patients. The primary objective of this study was to determine the optimal cutoff score on the DT for detecting psychological distress in cancer patients attending a rehabilitation center, by comparing the DT's scores with those of the Psychological Distress Inventory (PDI). The second aim was to explore the effectiveness of the DT as a screening tool for psychological distress in rehabilitative oncological setting.