Objectives It is well-known that tobacco smoking is related to various disease entities including chronic obstructive pulmonary disease, inflammation, cardiovascular disease, and neoplasms. The prohibition of smoking is important for the protection of these health problems. Regarding leptin, ghrelin, glucagon-like peptide 1 (GLP-1), and nerve growth factor (NGF) levels, correlations with the smoking are suggested but the reports on the effects after smoking cessation are not sufficient. Method The changes of plasma levels of leptin, ghrelin, GLP-1, and NGF levels were analyzed after quitting smoking in Korean adults. Eleven participants succeeding in quitting smoking among 37 male smokers were included in the final analysis. The plasma levels of NGF, leptin, ghrelin, and GLP-1 were measured before and after 8-weeks period of smoking cessation. Results The plasma level of leptin increased after 4 weeks of smoking cessation. In addition, the plasma level of NGF increased after 8 weeks of smoking cessation (p < 0.05). Conclusion Our results suggested that smoking cessation induces increases in leptin and the NGF level after smoking cessation. Many toxic materials including nicotine in the cigarette may be related to these changes of plasma level of leptin and NGF, playing a key role in neurogenesis and synaptic plasticity.