OBJECTIVES: To identify factors related to adherence after a multifactorial intervention in patients with COPD. METHODS: Design: Randomized Controlled Trial (ISRCTN 15106246) Patients: 146 subjects randomly allocated (random blocks of 4 patients) in two groups (intervention group-IG, control group-CG). Intervention components: • Motivational aspects: beliefs-behaviour about COPD (group and individual interviews). • Cognitive aspects: information about illness • Skills: inhaling techniques training Follow-up: 1 year, 5 visits/group. Primary Outcome: adherence (pill/doses count); Secondary Outcomes: functional status (spirometry), quality of life (Saint George Respiratory Questionnaire-SGRQ); Independent variables: intervention, age, sex, educational level, comorbidity, COPD severity stage (SEPAR guidelines), prescribed medication. Statistical analysis: Four partial logistic regression models, fixed- and random effects estimation, were carried out, a final model was built considering them. Statistical packages SPSS 15.0 and Stata 11.1. RESULTS: Predominance of males (91.8%), mean age 69.08 years (CI95%,67.58-70.44); low cultural level (78.1%), 32.2% current smokers (62.84 pack-years  [CI95%,55.34-70.34]), Body Mass Index 30.78 kg/m2 (CI95%,28.78-32.78), 81.2% mild-moderate severity stage, predominance of obstructive respiratory pattern; FEV1 (mean)= 67.58% (CI95%,64.58-71.08), 0.87 exacerbations/year [CI95%, 0.68-1.06]. Pharmacological treatment: inhaled-beta2-adrenergic (80.1%); inhaled-anticholinergic (77.4%); inhaled-corticosteroids (70.5%); mucolitycs (11.6%); xanthine (8.2%); oxygen therapy (4.8%); oral-corticosteroids (0.7%). Adherence was 41% (41.2CG/40.8IG). Both groups were similar at baseline. Drop out was 28.8%. Intention to treat analysis. Adherence increased significantly in IG (p=0.046), NNT=6.37 (CI95%,3.25-142.8). Factors related to adherence: intervention (OR=1.88, CI95%,1.01-3.52), number of exacerbation (OR=0.66,CI95%,0.48-0.91), number of visits to health centre (OR=0.93,CI95%,0.87-1.00), severity (OR=0.677,CI95%,0.43-1.04), number of devices (OR=2.4,CI95%,1.09-5.30), SGRQ-Activity scale (OR=0.978,CI95%,0.95-1.00), SGRQ-Impact scale (OR=1.03,CI95%,1.00-1.06), inhaled-beta2-adrenérgic (OR=0.16, CI95%,0.059-0.43), xanthine (OR=0.199, CI95%,0.05-0.77). Rho coefficient=6.07x10-6 (p=0.498). CONCLUSIONS: The more adherent patient was that who showed a lower number of visits to health centre, exacerbations, number of devices, level of severity, and impact on daily activities but with higher disease impact. The beta-2-adrenergic and xanthine treatment are associated with no adherence.