Tissi is a comune in the Province of Sassari in the Italian region Sardinia, located about 170 kilometres northwest of Cagliari and about 6 kilom…Tissi is a comune in the Province of Sassari in the Italian region Sardinia, located about 170 kilometres northwest of Cagliari and about 6 kilometres south of Sassari. As of 31 December 2004, it had a population of 2,017 and an area of 10.3 square kilometres.