CJ is a post-doc fellow (SFRH/BPD/115169/2016) funded by Fundação para a Ciência e Tecnologia (FCT), reimbursed by Fundo Social Europeu and by national funds of MCTES. This work was funded by ERDF (European Regional Development Fund) through the operations: POCI-01-0145-FEDER-029130 ('mINSPIRERS—mHealth to measure and improve adherence to medication in chronic obstructive respiratory diseases—generalisation and evaluation of gamification, peer support and advanced image processing technologies') cofunded by the COMPETE2020 (Programa Operacional Competitividade e Internacionalização), Portugal 2020 and by Portuguese Funds through FCT (Fundação para a Ciência e a Tecnologia). Objective We aimed to compare patient's and physician's ratings of inhaled medication adherence and to identify predictors of patient-physician discordance. Design Baseline data from two prospective multicentre observational studies. Setting 29 allergy, pulmonology and paediatric secondary care outpatient clinics in Portugal. Participants 395 patients (≥13 years old) with persistent asthma. Measures Data on demographics, patient-physician relationship, upper airway control, asthma control, asthma treatment, forced expiratory volume in one second (FEV 1) and healthcare use were collected. Patients and physicians independently assessed adherence to inhaled controller medication during the previous week using a 100 mm Visual Analogue Scale (VAS). Discordance was defined as classification in distinct VAS categories (low 0-50; medium 51-80; high 81-100) or as an absolute difference in VAS scores ≥10 mm. Correlation between patients' and physicians' VAS scores/categories was explored. A multinomial logistic regression identified the predictors of physician overestimation and underestimation. Results High inhaler adherence was reported both by patients (median (percentile 25 to percentile 75) 85 (65-95) mm; 53% VAS>80) and by physicians (84 (68-95) mm; 53% VAS>80). Correlation between patient and physician VAS scores was moderate (r s =0.580; p