Smokers willing to quit, with 10 teeth or more, and with periodontitis (30% or more of their teeth with proximal attachment loss ≥ 5 mm) were enrolled in the study. All subjects received periodontal treatment and concurrent smoking cessation therapy. Smoking cessation therapy was performed by a team comprising physicians, nurses, a psychologist and dentists, and consisted of four 1-h counselling lectures, psychologist-assisted cognitive behavioral therapy, nicotine replacement therapy and medication (bupropion or varenicline). Smoking cessation motivation was reinforced by dentists at the maintenance sessions, by means of motivational interviewing techniques. Periodontal therapy consisted in full-mouth supra and subgingival scaling and root planing (with curettes and ultrasonic scaler); oral hygiene instruction and motivation and removal of intra-oral plaque retentive factors. Further, periodontal maintenance was performed every 3 months.