The paper describes the effect of cutting parameters and tool geometry on the surface quality after machining of an Al/CFRP (aluminium alloy/ Carbon Fibre Reinforced Plastics) sandwich structure. A two-layer sandwich structure made of an EN AW 2024 aluminium alloy and Carbon Fibre Reinforced Plastics (CFRP) was examined. The experiment used the process of peripheral milling. The experiment investigated the effects of cutting speed (vc), feed per blade (fz) and helix angle (λs) on surface quality as defined by differences in the height of materials. It was also analysed how the machining conditions described above affected the values of cutting force components. In the experimental stage of the study, uncoated, double-bit carbide mill cutters with working diameter Dc = 12mm and a variable helix angle (λs = 20˚, λs = 35˚, λs = 45˚) were used. The results have shown that cutting parameters and tool geometry do affect the surface quality and cutting forces after milling of the sandwich structure. The lowest material height difference was achieved when machining with the helix angle λs = 45˚, cutting speed vc = 300m/min and feed per blade fz = 0.08mm/blade. The highest material height difference occurred after machining under the following conditions: vc = 300m/min, fz = 0.08mm/min, λs = 20˚. The minimum cutting force value was obtained for cutting parameters: vc = 80m/min, fz = 0.08mm/blade during milling with the helix angle λs = 45˚. The maximum cutting force was recorded during machining with the helix angle λs = 20˚, cutting speed vc = 400m/min and feed per blade fz = 0.08 mm/blade.