Quality of life has been found to be impaired both in patients with asthma and in patients with allergic rhinitis, but the relative burden of these diseases has not been investigated. We analyzed answers to the SF-36 questionnaire from 850 subjects recruited in two French centers participating in the European Community Respiratory Health Survey, a population-based study of young adults. Both asthma and allergic rhinitis were associated with an impairment in quality of life. However, 78% of asthmatics also had allergic rhinitis. Subjects with allergic rhinitis but not asthma (n = 240) were more likely than subjects with neither asthma nor rhinitis (n = 349) to report problems with social activities, difficulties with daily activities as a result of emotional problems, and poorer mental well-being. Patients with both asthma and allergic rhinitis (n = 76) experienced more physical limitations than patients with allergic rhinitis alone, but no difference was found between these two groups for concepts related to social/mental health. As asthma was not found to further impair the quality of life in subjects with allergic rhinitis for concepts related to mental disability and well-being, and as subjects with asthma often also suffer from allergic rhinitis, further studies on quality of life in asthma should ensure that the impairment in quality of life attributed to asthma could not result from concomitant allergic rhinitis.