Chem. mechanisms are used in 3D air quality models as well as for modeling lab. expts. Depending on the application the required detailedness of the mechanism differs. The mechanism generation program CHEMATA (Chem. Mechanism Adaptation to Tropospheric Applications) is able to generate explicit or lumped mechanisms according to the wishes of the user. In this work CHEMATA is applied for investigating the influence of different designs of mechanisms on the simulation results in a boxmodel study.