A stretch of the Tsna forms a border between Kuvshinovsky and Ostashkovsky Districts, and a short stretch north of the first one forms the border between Kuvshinovsky and Firovsky Districts. North of this stretch, the Tsna enters Firovsky District and gradually turns northeast.
A part of the Tsna marks the boundary between Kuvshinovsky and Ostashkovsky Districts, while a short section north of it delineates the border between Kuvshinovsky and Firovsky Districts. Beyond this stretch, the Tsna flows into Firovsky District and gradually changes its course to the northeast.