Today most catalytic converter designs have monolith-type substrates. Many of these designs use more than one monolith, due to different catalyst loadings or constraints on the manufacturing or coating of long monoliths. There is usually an open space between the monoliths.The flow distribution in the catalytic converter depends on the cone geometry of the catalytic converter, the space between the monoliths and their design. A connection between the flow distribution and the high conversion rate and the good long term stability is supposed.This paper presents the results of a study of the influence of space between monoliths, cone geometry and monolith length, on flow distribution, catalytic converter conversion rate and backpressure. The conversion rates for HC, CO and NOx at different engine load levels have been investigated.It was possible to determine a significant influence of the inlet cones and the space between monoliths on the flow distribution in the catalytic converter. It was not possible to ascertain an influence of these geometric changes on conversion rates of a non-aged catalytic converter.