Abstract Background The CohRTA multicenter study aims to characterize patients undergoing a first treatment for alcohol use disorder (AUD). The objective is to analyze sex-specific differences in the comorbidity of AUD when starting the first treatment for the disorder. Methods A multicenter study was carried out between 2014 and 2021 in 6 public centers in Spain. Sociodemographic characteristics were collected, variables related to alcohol consumption, medical comorbidity according to Cumulative Illness Rating Scale-Substance Abuse (CIRS-SA), antecedent of psychiatric comorbidity, general blood test and screening for drugs in urine. Logistic regression models were used to establish associations. Results A total of 896 patients (634 M, 262 W) were included. Median age at admission was 48 years IQR:41–56 years. Men reported beginning regular alcohol consumption at an earlier age and drank more alcohol. The most frequent medical comorbidities were hepatic, respiratory, vascular and neurological. The median number of affected systems was three, with no differences between men and women. However, depressive disorder was more frequent in women. In the multivariate analysis, women were up to 4 times more likely to have a major depressive disorder, elevated ESR and elevated total cholesterol than men. Men started alcohol consumption earlier, had a higher body mass index (BMI), a higher probability of using cocaine and a higher frequency of GGT and bilirubin alteration than women. Conclusion Differences by sex were found among individuals beginning first treatment for AUD. These differences must be taken into account when designing specific therapeutic strategies for men and women.