Livers, kidneys and muscles of large herbivorous animals: the roe deer (Capreolus capreolus), red deer, (Cervus elaphus) and fallow deer (Dama dama), collected in Northern Poland, were the subject of our investigation. The radioactivity concentration of ²³⁸U ranged widely between 2.49±0.18 and 69.37±5.45 mBq·kg^-1 w.w. There was no correlation between the accumulation of uranium and the analyzed tissues and organs. The values of ²³⁴U/²³⁸U activity ratio in analyzed samples were between 0.61±0.08 and 1.41±0.26, while most of the samples had ratios close to 1. The concentration of ^239+240Pu in the analyzed tissues decreased in the order kidney > muscle tissue > liver. The average radioactivity concentrations of ^239+240Pu ranged between 0.18±0.04 mBq·kg^-1 ww in muscle and 2.77±0.60 mBq·kg^-1 ww in kidneys. As statistically checked, the sampling location (ROLP Białystok, Gdańsk, Olsztyn, Szczecin, Szczecinek, Toruń), sex, age, and animal species did not influence the uranium and plutonium concentrations of the analyzed samples.