This paper presents an experimental study of the characteristics of Non-Newtonian fluids flow thorugh different diffuser geometries. The main geometrical studies were ; the diffuser expansion angle and the diffuser length. The overall area ratio for all diffusers tested was kept constant during the experiments. A capillary tube viscometer was used for measur-ing the rheological properties of the Non-Newtonian C.M.C. solutions. These properties are; the flow behaviour index and the consistency coef-ficient. The effect of these rheological properties on the static pres-sure rise coefficient, for different values of the diffuser inlet Reynolds number, was investigated. The results indicate that the concentration of the polymer solution, the flow Reynolds number, and the diffuser geometry have an effect on the diffuser performance.