A radiation image storage panel composed at least of a phosphor layer containing energy-storable phosphor particles and a light-reflecting layer provided on one side of the phosphor layer, in which the energy-storable phosphor particles are composed of at least two kinds of particles having different mean sizes, one of which is composed of smaller particles having a mean size of 2.0 to 4.0 .mu.m and the other of which is composed of larger particles having a mean size of 6.0 to 15 .mu.m, and a weight ratio between the smaller particles and the larger particles is in the range of 10:90 to 50:50 (former:latter), and in which the light-reflecting layer gives a scattering length of 5 .mu.m or less (the scattering length is for a stimulating light).