Background: Thirty percent of cancer patients are reported to suffer from psychological distress which detracts from treatment adherence, but that is often underestimated in clinical settings. HADS is one of the validated scales for screening emotional distress in cancer patients. However, it is not used widely because it is cumbersome to score. DIT is a 2-item (the Distress and the Impact) self-report questionnaire, but is not well verified. Methods: One hundred and seventeen patients were enrolled between 2011.5.1 and 2012.3.31 and 95 were eligible. Median age was 54 years (range 31–77). The numbers of completed questionnaires (HADS & DIT) at (a) pretreatment, (b) 3 months, and (c) 6 months were 95, 80, and 70, respectively. No patients relapsed during the investigated period. Results: 1) Areas under the curve of receiver operating characteristic curves for Distress and Impact with respect to HADS positivity were 0.855 and 0.875 respectively. At Distress ≥4 and Impact ≥2, sensitivity, specificity, positive predictive value, and negative predictive value were 0.818 (95% confidence interval (CI): 0.707–0.898), 0.875 (95%CI: 0.739–0.945), 0.9 (95%CI: 0.786–0.957), and 0.778 (95%CI: 0.637–0.875), respectively. 2) In each patient, the mean scales of (b) were significantly reduced in HADS (mean 3.2; p<0.0002) and in Distress (mean 1.7; p<0.0001), but not in Impact (mean 0.66; p=0.072) compared with (a). Those of (c) were significantly reduced in HADS (mean 4.5; p<0.0001), in Distress (mean 2.3; p<0.0001), and in Impact (mean 1.09; p=0.031) compared with (a) (Student’s paired t-test). Conclusions: 1) DIT is a reliable tool for ruling out clinical psychiatric distress. 2) For the first 6 months of treatment, mental mood would have a tendency to be improved, but not completely. Therefore, gynecologic oncologists should screen psychiatrically distressed patients by DIT and introduce them to psychiatric treatment early in the initial treatment. Clinical trial information: 000005727.