A pneumatic radial tire for passenger vehicles, the pneumatic radial tire comprising a carcass toroidally spanning between a pair of bead portions, the carcass including plies of radially arranged cords, wherein a sectional width SW of the tire is less than 165 mm and a ratio SW/OD between the sectional width SW and an outer diameter OD of the tire is 0.26 or less, at least one noise reducer is provided on an inner surface of the tire, assuming that when the tire is mounted on a rim and filled with a prescribed internal pressure in a load-free state, there are defined, in a tire width direction cross section, a center region and shoulder regions, the center region being a tire width direction region accounting for 50% at a tire width direction middle between ground edges, the shoulder regions being tire width direction regions accounting for 25% each on both tire width direction outer sides relative to the center region, the noise reducer is a sponge material; characterised in that the noise reducer is provided on the inner surface of the tire at least in the center region and the shoulder regions, and on the tire inner surface in the region on the tire width direction outer side of each of the shoulder regions; in that among thicknesses of the noise reducer measured in a direction perpendicular to the inner surface of the tire, a maximum thickness Tc in the center region is larger than a maximum thickness Ts in the shoulder regions; and in that the thickness of the noise reducer in the region on the tire width direction outer side of each of the shoulder regions is substantially constant and substantially equal to the thickness of the noise reducer at the tire width direction outer edge of each of the shoulder regions, or the thickness of the majority of the noise reducer in the region on the tire width direction outer side of each of the shoulder regions is substantially equal to the maximum thickness of the noise reducer in the center region. a sectional width SW of the tire is less than 165 mm and a ratio SW/OD between the sectional width SW and an outer diameter OD of the tire is 0.26 or less, at least one noise reducer is provided on an inner surface of the tire, assuming that when the tire is mounted on a rim and filled with a prescribed internal pressure in a load-free state, there are defined, in a tire width direction cross section, a center region and shoulder regions, the center region being a tire width direction region accounting for 50% at a tire width direction middle between ground edges, the shoulder regions being tire width direction regions accounting for 25% each on both tire width direction outer sides relative to the center region, the noise reducer is a sponge material; characterised in that the noise reducer is provided on the inner surface of the tire at least in the center region and the shoulder regions, and on the tire inner surface in the region on the tire width direction outer side of each of the shoulder regions; in that among thicknesses of the noise reducer measured in a direction perpendicular to the inner surface of the tire, a maximum thickness Tc in the center region is larger than a maximum thickness Ts in the shoulder regions; and in that the thickness of the noise reducer in the region on the tire width direction outer side of each of the shoulder regions is substantially constant and substantially equal to the thickness of the noise reducer at the tire width direction outer edge of each of the shoulder regions, or the thickness of the majority of the noise reducer in the region on the tire width direction outer side of each of the shoulder regions is substantially equal to the maximum thickness of the noise reducer in the center region.