Research has shown that financing drug therapy increases smoking abstinence rates, although most of these studies have been carried out in the private healthcare setting. The aim of this work is to assess the effect of subsidized pharmacological treatment on smoking cessation rates by the Spanish public healthcare system.A pragmatic, randomized, clinical trial was performed by clusters. Randomization unit was the primary healthcare center and the analysis unit was the patient. Smokers consuming ≥10 cigarettes/day were randomly assigned to an intervention group that received financed pharmacological treatment or to a control group that followed usual care. The main outcome was self-reported or CO-confirmed continuous abstinence at 12 months. The main outcome, continuous abstinence rates (%), were compared between groups at 12 months post-intervention. A model was adjusted using mixed-effect logistic regression.A total of 1154 patients were included from 23 healthcare centers. In the intention-to-treat analysis, self-reported abstinence after 12 months in the control and intervention groups, respectively, was 9.6% (37/387) and 15.4% (118/767) (gender-adjusted OR=1.75; 95% CI: 1.1-2.8); for CO-confirmed abstinence the corresponding values were 3.1% (12/387) and 6.4% (49/767) (gender-adjusted OR=1.72; 95% CI: 0.7-4.0). Pharmacological treatment use was 35.1% (136/387) in the control group, and 58.3% (447/767) in the intervention group (adjusted OR=4.25; 95% CI: 1.8-9.9).Subsidizing pharmacological treatment for smoking cessation increases self-reported or CO-confirmed abstinence rates under realistic conditions in the primary care setting of the Spanish public health system.