Background: Gingival recession is significantly more common among smokers, while cigarette smoking has been shown to negatively influence healing following periodontal therapeutic procedures as compared to non-smokers. The objective of this study was to evaluate the influence of cigarette smoking on the outcome of coronally positioned flap (CPF) in the treatment of Miller Class I gingival recession defects. Materials and Methods: Ten current smokers (≥10 cigarettes daily for at least 5 years) and 10 non-smokers (never smokers), each with one 3 to 4-mm Miller Class I recession defect in an upper canine or bicuspid, were treated with CPF. At baseline and 6 months, clinical parameters, probing depth (PD), clinical attachment level (CAL), recession depth (RD), and apico-coronal width of keratinized tissue (KT) were determined. Results: Intra-group analysis showed that CPF was able to reduce RD and improve CAL in both groups (p<0.001). Intergroup analysis demonstrated that smokers presented greater residual RD at 6 months and lower percentage of root coverage (60.09% versus 76.05%; p<0.05). No smokers obtained complete root coverage compared to 30% of non-smokers (p<0.05). Conclusion: Within the limits of present study, it can be concluded that cigarette smoking may present negative impact on root coverage outcome by CPF as compared to non-smokers and therefore represent one more challenge to periodontal plastic therapy.