The purpose of the study was cross-validation of Functional Transcranial Dopler (fTCD) with Single Photon Emission Computed Tomography (SPECT) during complex activation paradigm in order to demonstrate that fTCD is non-invasive, reliable, easy-to-use, inexpensive method, which can be used as complementary tool in comparison with SPECT and other functional neuroimaging methods. Further on, fTCD is a practical and safe method in evaluation with SPECT which includes radiation exposure and is time-consuming. This study suggests that fTCD is sensitive method with high temporal resolution and can be used for detecting brain activation. Bilateral continuous middle cerebral artery (MCA) monitoring of 60 healthy, right-handed subjects with fTCD was performed while the subjects underwent an activation task with visuospatial elements, and the hemispheric blood flow velocity increase was calculated. Identical stimulus and response patterns were used in the subgroup of 15 subjects, which underwent SPECT, and the hemispheric perfusion increase was calculated. Statistical analysis showed significant correlation between fTCD and SPECT (r=0,5608; P=0,030; r2=0,3154) for: blood flow velocity (BFV) in the right MCA during activation-measured with fTCD and relative right-sided perfusion increase-measured with 99mTc-HMPAO SPECT. Results suggest that both methods only partially measure same features related to brain activation in specific cortical areas. Statistically significant and proportional correlation between activation and baseline measurement results was found for both methods according to the side (P<0,001, respectively). Significant non-proportional correlation of relative increase was found for all (except for SPECT right-side relative increase) which suggests that certain level of stability (plateau) during activation was achieved and that activation paradigm was correctly selected. Both methods (fTCD and SPECT) succeeded in discriminating brain activation. Statistically significant increase of cerebral blood flow was detected by fTCD and SPECT (P<0,0001), suggesting that both methods are sensitive for investigation of close relationship between brain activity and cerebral blood flow.