Background: Atherosclerosis is well known related to age and certain cardiovascular diseases. Aging is one reason of arteries function deterioration which can cause loss of compliance and plaque accumulation, this effect increases by the presence of certain diseases such as hypertension and diabetes disease. Aim: To investigate the reduction of blood supply to the brain in patients with diabetes and hypertension with age and the role of resistive index in the diagnosis of reduced blood flow. Method: Patients with both diseases diabetic and hypertension were classified according to their age to identify the progression of the disease and factors influencing the carotid artery blood flow. By using ultrasound and standard Doppler techniques, the following parameters were measured, lumen Diameter (D), Intima – media thickness (IMT), peak systolic velocity (PSV), end diastolic velocity (EDV), Pulsatility Index (PI), Resistive Index (RI), velocity gradient, and the flow rate. Results: Results show that a small insignificant increase in the lumen diameter (3.49%), (p value > 0.05) between the old age group and the younger group (35- 55) and (56-75) year old. A significant increase in the intima-media (IMT) thickness, end diastolic velocity (EDV) and RI between both age groups was (33.78%), (-31.76%) and (10%) respectively with significant (p value <0.05). A large reduction for old age group in peek systolic velocity (PSV) (-19.71%), Pressure gradient (-31.11%) and flow rate (-20.91%) with (p>0.05) but all were statistically close to significance. Conclusion: The increased thickness in IMT did not influence the lumen diameter significantly. RI has the prime effect in the reduction of the blood flow which influenced blood supply to the brain and can indicate the effectiveness of intima media thickness on flow impairment. The changes in PSV, EDV, RI, and PI are also related with reduced compliance