Factors influencing coffee consumption in the importing countries vary widely. The popularity and worldwide appeal of coffee, which stems from its unique flavor, make it currently one of the most desirable and frequently consumed beverages. Coffee beans found on the market are produced from two different species of Coffea genus: Coffea arabica and Coffea canephora syn. Coffea robusta. The objective of current study was to determine the content of caffeine in Green coffee beans of two varieties (Coffea Arabica Santus from Brazil and Coffea Canephora :Rubusta) from Vietnam as well as coffee beans roasted in three roasting degrees (light, medium and dark) . The coffee varieties analyzed in this study (Vietnam, Brazil) were obtained from importer coffee in Iran. Green beans of each coffee variety were ground with coffee mill and then roasted. Three different roasting degrees (coffee roasting at 250 oC for different roasting times - 8, 15 and 20 min called: light, medium and dark roasted coffee samples. Caffeine in coffee samples was extracted with water and magnesium oxide. After filtering the caffeine content in extracts was determined with HPLC and separation was performed on RP-C18 column by isocratic elution with UV detection in 272 nm. The caffeine concentrations were comparable with other reported where it is observed that the concentration depends principally on the genus or variety of coffee and the caffeine extraction method from coffee beans. Caffeine concentration in Arabica roasted coffee beans between 1.24 and 2.54% (w/w) and for Robusta was between 2.08-3.37 %. The results revealed that the content of caffeine content of different coffees vary depending on the coffee variety and are affected by the roasting. Light roasted Brazilian Arabica coffee contained the highest overall content of caffeine in all coffees, which exhibited a decrease with intensified roasting.