OBJECTIVES: To test the characteristics of a QUICK Questionnaire-Short version (Q10) as diagnostic instrument for wearing-off phenomenon (WO) in Parkinson’s disease (PD) patients. METHODS: Observational, cross-sectional, multicenter, and national study developed in clinical practice. The study was developed in two consecutive phases: I, to determine the sensitivity and specificity of Q10; and II: to assess the usefulness (investigators) and the ability and ease of use (patients) of Q10 questionnaire. Furthermore, the prevalence of WO among PD patients consecutively attending the specialist was also assessed (phase II). Patients ≥30 years old at the onset of the disease with ≤5 years from diagnosis and under treatment were selected. RESULTS: In phase I, 162 patients were included, 67.4±9.7 years old, 53.8% males, and 3.1±1.4 years from diagnosis. Most of them (85%) were in Hoehn-Yahr stage 2-3. WO was presented in 64.8% (33.3% mild; 31.5% moderate/severe). Q10 was completed in 6.6±4.9 minutes. With two positive responses the Q10 showed good sensitivity (90%) and moderate specificity (70%) and with 3 positive responses both values reached an arbitrarily hypothesized 75% threshold (sensitivity: 81%; specificity: 75%). The mean usefulness Q10 score was good [7.3 (1.6), scale 1-10]. In phase II, most patients considered Q10: easy to understand (80.6%), reflect their present situations (78.8%), and useful to communicate discomfort to the doctor (80.6%). The prevalence of WO among the total PD patients attending to the neurologist was of 59.0%, higher in males (64.9%), Hoehn-Yahr staging (80%, 3-4 stage) and in patients with more time of PD evolution (71.9%). CONCLUSIONS: The Q10 is a useful instrument for screening and diagnosis of WO, showing good sensitivity and specificity, as well as, good usefulness, ability and ease to use. Almost two out of three PD patients attending to the neurologist presented WO.