"Lac des Pas Perdus" is located in the central part of the Laurentides Wildlife Reserve.

The surface of Pas Perdus Lake is usually frozen from the beginning of December to the end of Pikauba, however the safe circulation on the ice is generally made from mid-December to mid-Pikauba.

The mouth of Lac des Pas Perdus is located approximately 2.7 kilometres (1.7 mi) northeast of the boundary of the administrative regions of Saguenay–Lac-Saint-Jean and Capitale-Nationale.

This lake has a bay stretching for 1.0 kilometre (0.62 mi) to the east where the outlet (from the north) of Lac Éperon flows; the narrowing of the lake at the entrance to this bay is formed by a peninsula attached to the north shore and another coming from the south shore.

The toponym "Lac des Pas Perdus" was formalized on December 5, 1968, by the Commission de toponymie du Québec.