The aim of this study was to assess the feasibility, validity, reliability and sensitivity to change of a Spanish version of the Dermatology Life Quality Index (DLQI) in patients with mild to moderate eczema and psoriasis who were treated with topical corticosteroids. The final study sample comprised 237 patients (48% eczema). Discriminant validity was tested by comparing patients' scores with those of a random sample of the general population (n = 100), and convergent validity by analysing correlations between DLQI scores, measures of clinical severity, and domain scores on the Nottingham Health Profile (NHP). Internal consistency and test–retest reliability were tested in clinically stable patients (n = 94), and responsiveness in a clinically unstable group (n = 143) initiating treatment with topical corticosteroids. Patient scores were significantly higher than general population scores (4.3 vs. 0.27, P < 0.001). Correlations with NHP domains ranged from 0.12 to 0.32, and there was significant correlation with clinical measures (r = 0.26, P < 0.001). Reliability was good (Cronbach's alpha = 0.83; intraclass correlation coefficient = 0.88), and the instrument proved responsive to change (effect size for the total group of de novo patients = 0.70), though the great majority of changes occurred in items 1 and 2. The NHP Emotional Reactions and Mobility domains were more responsive than some DLQI domains. In clinical trials of treatments for mild to moderate eczema and psoriasis, it is likely that only items 1 and 2 of the DLQI will be needed, and it is probably advisable to include generic instruments alongside the DLQI.