Inherited lysosomal storage disorders are caused by the deficiency or importantly lowered activity of one of the lysosomal enzymes, leading to the storage in the lysosomes the not degraded high-molecular substrates, among others: mucopolysaccharides, glycolipids, oligosaccharides and glycoproteins. Thin-layer chromatography of urine oligosaccharides allows reliable and fast diagnosis of some lysosomal storage disorders e.g. alpha-mannosidosis, fucosidosis, sialidosis, galactosialidosis, Schindler disease, GM1-gangliosidosis, GM2-gangliosidosis (Sandhoff type), Pompe disease, Salla disease, mucolipidosis II and III. We are presenting a modification of the Humbel and Collart's method of TLC of urine oligosaccharides. The principle of our modification is to introduce of the preliminary desalting step of the urine on the columns containing anionit BioRad AG 1 x 8 and cationit Dowex 50 x 8-200.