A process for producing lactose-free dairy products is suggested, comprising the following steps: (a) Hydrolysis of a starting milk while adding lactase; (b) Nanofiltration of the hydrolysis product for producing a first permeate P1 and a first retentate R1; (c) Reverse osmosis or nanofiltration of the first permeate P1 for producing a second permeate P2 and a second retentate R2; (d) Mixing the first retentate R1 with such an amount of the second permeate P2 and the retentate R2 that a standardized dairy product is obtained, the content of proteins and minerals of which correspond to the one of the starting milk.