Atomic force microscopy allows observation of the adhesive surface and characterization of the adhesive behavior on a nanoscale level, providing new and important information about the behavior of pressure-sensitive adhesives (PSAs). In this research PSAs consisting of poly(ethylene propylene) and the n-butyl ester of abietic acid are studied. Results of nanoindentation measurements indicate two different types of behavior: a viscoelastic behavior in the tackifier-rich domains and a more highly dissipative response in the matrix with a gradual transition behavior in areas close to the interfaces between the domains and the matrix. The adhesive energy appears to be dictated predominantly by the tackifier-rich domains.