The present invention relates to a process for producing a disposable diaper by supplying a continuous web of flat material in a longitudinal direction for the forming of the side portions, forming first material clearances along a first cutting line at a side edge) of the web of flat material to produce contoured cutouts in the web of flat material, an imaginary parallel line PL, which is parallel to the longitudinal direction and placed at the point P of maximum extent of the cutout transversely in relation to the longitudinal direction, defining an outer sub-region and an inner sub-region of the web of flat material, folding the web of flat material about at least one first folding line running in the longitudinal direction, the folding line running within the outer sub-region, severing longitudinal portions of the folded web of flat material, undetachably fixing the portions of material to a respective longitudinal edge of a web for the main part of the diaper for the forming of side portions, forming second material clearances along a second cutting line, the second cutting line taking in the side portions and a respective longitudinal edge of the web for the main part of the diaper, and the second cutting line crossing the first cutting line in such a way that the second cutting line does not extend through the first folding line of the front and rear side portions.