( 9 9 m Tc)HMPAO is a radiopharmaceutical used for SPECT imaging of regional cerebral perfusion and for labeling cellular blood elements. The addition of methylene blue enhanced the stability of lipophilic ( 9 9 m Tc)HMPAO complex up to 3h after reconstitution, 86.9+/-4.2% compared to 49.8+/-8.9% for the non-stabilised complex and persists over time (86.2+/-3.5% after 15min compared to 78.2+/-4.0% after 3h). The method widely used for estimation of radiochemical purity is a standard chromatographic procedure which is quite time-consuming taking about 30min. Comparison of the more rapid and simple solvent extraction method with octanol, which needs only about 10min to complete, showed a good correlation with the chromatographic method (84.4+/-4.4% compared to 89.1+/-4.3%). Using ethyl acetate as solvent instead of octanol gave a slightly higher extraction rate of the lipophilic complex (91.5+/-5.5% compared to 89.1+/-4.3%). Further, the ethyl acetate extraction method results in an overestimation, extracting partly secondary complex. It is confirmed, that the stability of the lipophilic ( 9 9 m Tc)HMPAO complex can be increased with methylene blue. The octanol extraction method, using higher extraction volume (up to 3ml), is recommended as a fast and efficient approach for the quality control in daily clinical routine.