In an x-ray lens for focusing x-rays over a large energy range wherein the lens comprises a large number of lens elements, the lens elements have a quasi-parabolic profile Y(x) according to the equation Y(x)=x.sup.2/2[(r+f(x))] Wherein x represents the parabola axis, l/2r represents the half parameter of the parabola and f(x) represents a function different from zero.