In situ indoor gamma dose rate measurements were held in 79 dwellings by NaI(Tl) scintillation probe connected portable dose rate meter. For the building materials and impurities (nodules), spectrometric gamma analysis was applied by a high-resolution HpGe detector. For Ahmetce and Nusratli villages in Ayvacik/Canakkale (Turkey), the measured in situ indoor gamma dose rates and related indoor annual effective dose equivalents (AEDE(in)) were 3 and 3.3 times, and indoor excess lifetime cancer risks (ELCRin) were 4.25 and 4.68 times higher than those of the world averages, respectively. The used local rocks were mostly ignimbrite and dacitic-rhyolitic tuffaceous (Arikli tuff), and wall plasters were made of local soil. The highest in situ indoor gamma dose rates of the region belonged to Nusratli village due to the intense impurities (nodules) and hydrothermal alterations in Arikli tuff. Spectrometric gamma results revealed that K-40 has an important effect on the indoor gamma doses.