Widespread Neogene volcanism, mainly intermediate and rarely mafic and felsic in composition, was controlled by the extensional tectonic regime in western Turkey. The Karaburun and Cumaovasi volcanics are the cases for understanding the magma source(s) and petrological processes, producing the extension-related mafic and felsic volcanism. The Karaburun volcanics (KV) are mainly oriented north to south in the Karaburun peninsula and span a wide spectrum from basalt (20 Ma) to rhyolite (16 Ma), and younger trachyte and trachydacites (13 Ma). The products of the subaerial silicic volcanism (the Cumaovasi volcanics, CV; 17 Ma) which are represented by cluster of rhyolite domes, related pyroclastics occur within the NE-SW trending Cubukludag graben, and intermediate and mafic volcanic rocks are lack in this area. The lavas of the Cumaovasi volcanics are high silica rhyolites and rare dacites which are calc alkaline, peralumious and enriched significantly in LILE. Extremely low Sr, Ba values, extremely Eu depletions and very low La-N/Yb-N ratios are typical for the rhyolites of CV, similar to the topaz rhyolites. The Karaburun volcanics, with the exception of the minor alkaline basaltic and trachytic lavas, are mainly calc alkaline and metaluminous intermediate lavas. Sr-87/Sr-86 ratios of the KV and dacitic samples of CV are close to each other and range from 0.708 to 0.709; while Sr isotopic ratios of the rhyolites are significantly high and variable (0.724-0.786). Na-143/Nd-144 ratios of the CV and KV, except for the alkaline samples, are similar for both sequences vary from 0.51230 to 0.51242.