Introduction. Cardiothoracic surgery with a median sternotomy is an electing factor for the development of a hypertrophic scar. Hypertrophic scars, characterized by an increased vascularity, often result in aesthetic and functional problems. Smoking, due to its negative effects on vascularization, could therefore have an effect on scar healing. Objective. A prospective cohort study was conducted to evaluate the effect of smoking on scar healing after cardiothoracic surgery with a median sternotomy incision. Materials and Methods. One hundred patients who underwent cardiac surgery with a median sternotomy were divided into 3 groups: smokers, ex-smokers, and nonsmokers. Erythema values of the scar were measured with a colorimeter on 3 standardized parts of the scar. Scar evaluation was performed at 6 weeks, 3 months, 6 months, and 12 months after surgery. Results. During 1 year, a total of 90 patients were followed after a median sternotomy; 10 patients were lost to follow-up. There were 23 smokers, 52 ex-smokers, and 15 nonsmokers with an overall mean age of 61.5 ± 8.83 years. No significant difference in redness as a parameter for hypertrophic scarring was observed between the 3 groups. Nevertheless, a trend in favor of the smokers was seen, as they developed less hyperemic scars. The caudal part of the scar showed a significantly higher incidence of hypertrophy compared with the middle and cranial part of the scar (P < .001) at all time points. Conclusions. It is presumed that a large sample size with younger patients is needed to confirm the results herein. Furthermore, more caudally located skin, especially the subxiphoidal part, is prone to hypertrophic scarring and should, for that reason, be avoided in the incision.