Flow mismatch between blood and dialysate is invariably encountered during conventional hemodialysis, and this deteriorates diffusive mass transfer. A modification of a conventional dialyzer was conceived to prevent this mismatch. The modified dialyzer includes two independent blood flow regions (central and peripheral regions), which were achieved by redesigning the dialyzer cap. Resultantly, the blood stream was divided into two concentric dialyzer regions. Solutes clearances obtained using the modified dialyzers were compared with those of conventional dialyzers. Solutes clearances by conventional dialyzers were uniform, but solutes clearances by modified dialyzers were found to be dependent on the simulated blood split into dialyzer central and peripheral regions. Maximal clearances using the modified dialyzer were improved by up to approximately 7.6% for urea and 7.3% for creatinine, as compared with those of conventional dialyzers. More optimizations are required for clinical applications, but the finding that blood flowrates through central and peripheral fiber bundles can be easily regulated is encouraging.