Disclosed is a 2-methyl-2-pentenyl ester represented by the general formula (1) [wherein R represents a hydrogen atom or a hydrocarbon group having 1 to 9 carbon atoms which may have a substituent]. The compound has a new-type, unprecedented aroma and/or flavor, particularly a fruity, greenish or floral aroma and/or flavor. The compound can be added to a flavor or fragrance composition in an amount of 0.001 to 30 wt %. The flavor or fragrance composition can be added to a cosmetic product, a toiletry product, a bath agent, a food, a beverage or a pharmaceutical product in an amount of 0.0001 to 30 wt %. All of the compounds of the general formula (1) are novel, except for those compounds of the general formula (1) wherein R represents a methyl group, an isopropyl group, a phenyl group or a mesityl group.