[en] Estimates of the committed effective dose (E₅₀) from an inhalation of a radionuclide depend strongly on the absorption type and AMAD of inhaled particles. A misuse of these parameters can result in a significant error in the evaluated value of the E₅₀. In this study, the uncertainties in E₅₀ caused by a misjudgment of the absorption type and AMAD of inhaled ⁶⁰Co were evaluated for various bioassay types and measurement times after an inhalation. The considered dosimetric parameters and their ranges are as follows: M and S for absorption types in lungs; 0.1, 1, 5, 10 μm for AMAD sizes; 1-365 days for bioassay measurement times after an inhalation. The ratios of the evaluated E₅₀ with an assumption of the absorption type M and 5μm AMAD to the true E₅₀ were in the range of 0.37-3.50 for the lungs bioassay, 0.08-1.43 for the whole-body bioassay, 0.004-1.54 for the urine bioassay, and 0.01-1.68 for the feces bioassay. In order to minimize the uncertainty in the evaluated E50 when the absorption type and AMAD are uncertain, better bioassay types and measurement times were suggested