A method for measurement of the thickness of thin layers or determination of an element concentration of a measurement object. A primary beam is directed from an X-ray radiation source onto the measurement object. A secondary radiation emitted by the measurement object is detected by a detector and is relayed to an evaluation device. The primary beam is moved within a grid surface which is divided into grid partial surfaces as well as subdivided into at least one line and at least one column. For each grid partial surface a primary beam is directed onto the grid surface. A measuring spot of the primary beam fills at least the grid point. A lateral dimension of the measurement surface is detected and compared to the size of the measuring spot of the primary beam appearing on the measurement object, for size determination of the measurement surface of the measurement object.