ABSTRACT: BACKGROUND: According to some studies, almost 40% of depressive patients - half of them previously undetected - are diagnosed of bipolar II disorder when systematically assessed for hypomania. Thus, instruments for bipolar disorder screening are needed. The Mood Disorder Questionnaire (MDQ) is a self-reported questionnaire validated in Spanish in stable patients with a previously known diagnosis. The purpose of this study is to evaluate in the daily clinical practice the usefulness of the Spanish version of the MDQ in depressive patients. METHODS: Patients (n = 87) meeting DSM-IV-TR criteria for a major depressive episode, not previously known as bipolar were included. The affective module of the Structured Clinical Interview (SCID) was used as gold standard. RESULTS: MDQ screened 24.1% of depressive patients as bipolar, vs. 12.6% according to SCID. For a cut-off point score of 7 positive answers, sensitivity was 72.7% (95% CI = 63.3 - 82.1) and specificity 82.9% (95% CI = 74.9-90.9). Likelihood ratio of positive and negative tests were 4,252 y 0,329 respectively. LIMITATIONS: The small sample size reduced the power of the study to 62%. CONCLUSION: Sensitivity and specificity of the MDQ were high for screening bipolar disorder in patients with major depression, and similar to the figures obtained in stable patients. This study confirms that MDQ is a useful instrument in the daily clinical assessment of depressive patients.