The invention relates to a low-lactose and a lactose-free milk product and toa process for the production thereof.The lactose in the milk raw material is hy- drolyzed, proteins, minerals andsugars are separated into different fractions by themembrane technique, and a low-lactose or a lactose-free milk product iscomposed from the fractions. The invention provides amilk product the water therein originating from the original milk rawmaterial. In addition, useful by-products are produced in theprocess.