The invention relates to a mass balancing mechanism for balancing mass forces and/or mass torques of an internal combustion engine. The mass balancing mechanism comprises an unbalanced shaft (4) having shaft sections (6, 7) for generating the imbalance, two outer bearing journals (9, 10), and at least one inner bearing journal (5) that connects two of the shaft sections, at which bearing journals the unbalanced shaft is rotatably supported in associated bearing points (2, 1, 3) of the internal combustion engine. The inner bearing journal rebounds radially relative to the two shaft sections adjacent thereto and forms a radial plain bearing with the inner bearing point (2). According to the invention, the outer bearing journals should each form a radial roller bearing with the outer bearing points (1, 3).