The initiation and evaluation of treatment with biologics for psoriasis is based on the Psoriasis Area Severity Index (PASI) and/or Dermatological Life Quality Index (DLQI). However, these indices do not always correlate well, and changes in the DLQI do not always follow changes in the PASI. Based on data from the Danish national registry (DERMBIO), this study investigated the correlation between changes in PASI and DLQI in a cohort of patients with moderate-to-severe psoriasis treated with biologics or apremilast using Spearman's rank correlation analyses. The correlation analysis of 1,677 patients, of whom 276 had available data after 5 years, showed weak-to-moderate correlation between PASI and DLQI during a 5-year period and between changes in PASI and DLQI: 0.58 (p < 0.0001) for baseline to 3 months and 0.42 (p < 0.0001) for 3 to 12 months. The first question on "Symptoms and feelings" made up the largest proportion of the overall DLQI. The correlation between PASI and DLQI is weak-to-moderate and varies over time. Changes in PASI correlate weak-to-moderately with changes in DLQI during the first 12 months of treatment, with symptoms being the most important factor contributing to impaired quality of life.