Background: Smoking adversely affects the short-term outcomes of coronally positioned flap (CPF) root coverage procedures, but the long-term stability of this procedure in smokers has not been studied. The objective of this study was to evaluate the effect of smoking on the long-term outcomes of CPF in recession treatment. Methods: CPF was used to treat a Miller Class 1 defect in a maxillary canine or premolar in 10 current smokers (>= 10 cigarettes daily for >= 5 years) and 10 non-smokers (never smokers). At baseline and 6, 12, and 24 months, clinical parameters, including probing depth (PD), clinical attachment level (CAL), recession depth (RD), and width of keratinized tissue (KT), were determined. Results: Intragroup analysis showed that CPF failed to maintain the gingival margin at the initially achieved position. RD significantly increased in smokers (from 0.84 +/- 0.49 to 1.28 +/- 0.58 mm) and in non-smokers (from 0.22 +/- 0.29 to 0.50 +/- 0.41 mm) between 6 and 24 months. Further analysis showed that 50% of smokers and 10% of non-smokers lost between 0.5 and 1.0 mm of root coverage in the same period. Intergroup analysis showed that smokers had significantly greater residual recession (P = 0.001) at 24 months. Both smokers and non-smokers lost CAL and experienced decreases in KT. Conclusions: The long-term stability of CPF outcomes is less than desirable, particularly in smokers. Two years after a CPF procedure, smokers have significantly greater residual recession compared to non-smokers both statistically and clinically.78917021707