In a method for producing CsX:Eu stimulable phosphors and screens or panels provided with said phosphors as powder phosphors or vapor deposited needle-shaped phosphors suitable for use in image forming methods for recording and reproducing images of objects made by high energy radiation, said CsX:Eu stimulable phosphors are essentially free from oxygen in their crystal structure, wherein X represents a halide selected from the group consisting of Br, Cl and combinations thereof; and wherein the method further comprises the steps of mixing CsX with a compound or combinations of compounds having as a composition Cs.sub.xEu.sub.yX'.sub.x+.alpha.y, wherein the ratio of x to y exceeds a value of 0.25, wherein .alpha..gtoreq.2 and wherein X' is a halide selected from the group consisting of Cl, Br and I and combinations thereof; heating said mixture at a temperature above 450.degree. C.; cooling said mixture, and, optionally, annealing and recovering said CsX:Eu phosphor.