The aquatic species Ceratophyllum demersum and Myriophyllum spicatum were grown in a hydroponic system to analyze the activity of antioxidant enzymes and protein response under different cadmium concentrations. The behavior of the studied antioxidant enzymes (APX and POD) was affected by Cd-exposure and exhibited to some extent different activity. In comparison with control, the activity of APX and POD varied significantly (P<0.01) among Cd-treatments, where the increase in Cd-concentration coupled with an initial increase in the activity of both antioxidant enzymes and subsequent Cd-treatments caused a decline in the activity. Generally, the activity of APX found to be more pronounced in M. spicatum (4-8 fold of control) in comparison to C. demersum. The treated plants exhibited different protein patterns depending on the plant species, Cd- concentration and time of exposure. Protein synthesis appears to be more sensitive to cadmium in C. demersum, than other plants where, appearance of high molecular weight (138, 127, 112, 109 and 100 kDa) protein at 25mg/LCd, disappearance of 38 kDa proteins was recorded in all sets of experiment