This study investigated the effect of various roasting conditions on regular and decaffeinated green beans. Regular and decaffeinated green beans from Guatemala, Brazil, Ethiopia, and Colombia were prepared under light, medium, and dark roasting conditions. Analysis of the decaffeination-induced changes in nonvolatile compounds revealed that decaffeinated green coffee beans had significantly lower concentrations of trigonelline (25%) and total carbohydrates (16%) but a higher chlorogenic acid content (10-14%) than regular green coffee beans (bothp < 0.05). Flavor differences between regular and decaffeinated coffee were investigated by analysis of the volatile and nonvolatile compounds in roasted coffee beans. From the odor impact ratio values, 3-ethyl-2,5-dimethyl pyrazine, 5-methyl furfural, and guaiacol were primarily responsible for coffee flavor. 3-Ethyl-2,5-dimethyl pyrazine had 58% lower concentration in decaffeinated coffee than in regular coffee. This study is valuable in providing the chemical composition of decaffeinated coffee and way to improve the quality of decaffeinated coffee.