OBJECTIVES: to test the efficacy of two educational interventions to improve the inhalation techniques in patients with Chronic Obstructive Pulmonary Disease. METHODS: Design: Multicenter Randomised Controlled Trial ISRCTN60147249. Patients: 220 COPD patients (to detect a difference between groups of 25%, 80% statistical power, 95% confidence level, 40% expected losses), with inhaled treatment, written consent. Non-probabilistic consecutive sampling. Allocation: Patients were randomised using block randomization into three cohorts: InterA, IntervB, control. Variables: Primary outcomes: Performance of correct inhalation technique. Secondary outcomes: Pick flow, Baseline dyspnea index (BDI), Functional status (forced spirometry). Interventions: Intervention-A: Written information. A leaflet with the correct inhalation technique for the main inhaler devices used in our area. Intervention-B: Intervention-A + individual training (by instructors). Follow-up: 12 month, visits: baseline, 1 month, 3rd month, 6th month, 12th month. Statiscal analysis: Mean, frequency, 95% confidence interval at baseline. Number Needed to Treat for a benefit (NNT) was calculated. Intention to treat analysis. RESULTS: Predominance of males (85.5%), mean age 70.54 years (CI95%, 69.38-71.7); FEV1(mean)=54.2% (IC95%, 51.81-56.55), mixed respiratory pattern (62.5%). Severity stage: 11.4% mild, 47.4% Moderate, 41.4% Severe. Pharmacological treatment: inhaled-beta2-adrenergic (81.7%); inhaled-anticholinergic (76.3%); inhaled-corticosteroids (75.3%); mucolitycs (13.7%); xanthine (5%); oral-corticosteroids (0.9%). BDI: grade 2. There were no statistically significative differences between groups at baseline. Primary outcome:  The 88.1% of patients did not perform a correct inhalation technique: 88.5% with Handihaler, 83.3% with Turbuhaler, 81.7% with Accuhaler and 79.1% with pMDI. There were statistically significative differences between control and intervention A (p=0.023), NNT= 8.62 (IC95%, 4.63-62.5). There were statistically significative differences between intervention B versus control (p<0.0001), 1.74 (IC95%, 1.47-2.17). CONCLUSIONS: The knowledge about the correct performance of inhalation techniques is poor in patient with COPD. The performance of a correct inhalation technique improves with monitor training.