OBJECTIVES:  Atopic dermatitis (AD) is associated with substantial impairment of patients’ health-related quality of life (HRQoL). A new instrument, the AD Impact Questionnaire (ADIQ), was developed following FDA PRO Guidance (2009) to assess impact of AD on patients’ lives. The ADIQ was included in a Ph2 clinical trial and data from that trial was used to assess measurement properties. METHODS:  In a Ph2 clinical trial 209 patients aged 18–75y with moderate-to-severe AD (after initial screening and a 2-week topical corticosteroid [TCS] run-in period), were randomized to receive lebrikizumab 125mg Q4W, 250mg single dose (SD), 125mg SD, or placebo (PBO) plus twice-daily medium-potency TCS to all lesional skin for 12 weeks. Secondary analyses of screening, run-in, and Week 12 data, were used to evaluate item-level statistics, scaling structure, reliability and validity. Data from all arms were pooled to assess measurement properties of the ADIQ. Data from patients with stable disease, i.e. less than a meaningful change (6.6pts) on the Eczema Disease Severity Index (EASI), was used for analyses with multiple timepoints, e.g. test-retest. RESULTS:  203 (97%) patients completed the ADIQ at screening. It showed evidence of adequate reliability (α=0.76); reproducibility (ICC = 0.95); and validity, with the latter including moderate correlations with the Dermatology Life Quality Index (DLQI; r=0.84), and patient-reported components of SCORing Atopic Dermatitis [SCORAD; r=0.41 (pruritus) and 0.46 (sleep loss)] at screening. Concurrent correlation between the ADIQ and indices of disease severity, [overall SCORAD, EASI and Investigator Global Assessment (IGA)] was relatively low. However, change in ADIQ from screening to Week 12 readily detected minimal important differences in disease severity over the same time period, with SCORAD, EASI and IGA concordance indices ranging from 0.76 to 0.81. CONCLUSIONS:  Results suggest the ADIQ is a reliable and valid measure to assess treatment benefit on AD patients and can complement disease severity assessments.