Background: Online self-management programmes for asthma have recently become available. International guidelines suggest that the Asthma Control Questionnaire (ACQ) can be used in these programmes. In order to assess the current level of control and guide therapy, the same cut-off values are being used as in conventional asthma management. However, results might differ between different types of administration of the ACQ. Aims: To assess the agreement between an online self-administered version of the ACQ and an interviewer-administered version at a routine visit. Methods: Cross-sectional data from primary care asthma patients in the Asthma Control Cost Utility Randomized Trial Evaluation (ACCURATE) trial aged 18-50 years and prescribed inhaled steroids were analysed. We selected patients who self-administered an ACQ online and subsequently had an ACQ completed by a nurse practitioner within 7 days at a trial-related control visit. ACQ scores were calculated and agreement assessed by paired t-tests, Pearson's correlation coefficient and a Bland-Altman plot. Results: A total of 351 patients were eligible (68% female, mean age 40 years). The time interval between the two versions was 3.2 days. There was a significant difference of 0.14(95% CI 0.09 to 0.20; p<0.001) between the results of the online self-administered ACQ (mean 1.04 +/- 0.04) and the interviewer-administered ACQ results (0.90 +/- 0.04). The Pearson correlation coefficient was 0.79. The limits of agreement (-0.86, 1.14) exceeded the predefined minimal clinically important difference between results (+/- 0.5). The Bland-Altman plot therefore showed insufficient agreement. Conclusions: Assessment of asthma control by the ACQ is influenced by the type of administration. Our results suggest that better control of asthma is perceived when interacting with a caregiver than by online self-assessment.