There is a lack of evidence for the consistency between self-reported alcohol consumption (SRAC) and concentrations of ethyl glucuronide in hair (hEtG) among elderly patients treated exclusively for alcohol use disorder (AUD). Hence, this study assessed the consistency between these two measures in these patients. A total of 190 patients with AUD were assessed for SRAC using Form 90 and hEtG, 14 or 22 weeks after treatment conclusion. Patients were grouped according to SRAC (g/day) and corresponding hEtG concentrations (pg/mg): 0 and textless5 (abstinence), 0.1–14.3 and 5.0–9.9 (low consumption), 14.4–21.4 and 10.0–15.9 (moderate consumption), 21.5–59.9 and 16.0–30 (high consumption) and ≥60 and textgreater30 (excessive consumption). The extent of underreporting and overreporting was examined by crosstabulations, and inter-rater reliability was reported by kappa correlations. Associations and effect modification were examined by conditional logistic regression. Due to multitesting, p-values ≤0.01 were considered significant. Underreporting was found in 96 patients (50.5 and overreporting in 41 patients (21.6. The kappa coefficients varied between 0.19 and 0.34. HEtG was more likely to detect low, moderate and high alcohol consumption compared with SRAC (ORs between 5.1 and 12.6, all p-values textless0.01), but SRAC and hEtG did not differ significantly with respect to identification of abstinence (OR = 1.9, p = 0.05). Inconsistency between the outcome measures was found in a considerable number of the patients. More studies examining the consistency between SRAC and specific direct biomarkers of alcohol in this population seem warranted.