The invention relates to a continuously variable transmission for motor vehicles provided with a driving pulley (1) and with a driven pulley (2) around which is arranged a drive belt (3) which, at least when the transmission is operating, is clamped between two substantially conical pulley sheaves (4, 5) of the two pulleys (1, 2). The cone surface (10) of the pulley sheaves (4, 5) of the driving pulley (1) in a cross-section including the central pulley axis (9) is provided with a convex curvature having a radius of curvature (R10) that decreases in radially outward direction and the cone surface (10) of the pulley sheaves (4, 5) of the driven pulley (2) in a cross- section including the central pulley axis (9) is provided with a convex curvature having a radius of curvature (R10) that increases in radially outward direction.