Abstract: An apparatus for depositing organic layers on a substrate includes a gas-mixing device with one or more inlets, each for supplying a gas flow consisting of previously vaporized organic molecules that are conveyed by a carrier gas and have a molar mass greater than 300 g/mol or 400 g/mol, gas diversion elements which homogeneously mix the organic molecules in the carrier gas, and an outlet from which a homogeneous gas mixture discharges. The apparatus also comprises a conveying pipe which is connected to the outlet, and a gas inlet element that has a gas distribution volume, into which the conveying pipe leads and which has a gas outlet face that has gas outlet openings and faces a substrate holder for receiving the substrate. Furthermore, layers are deposited on the substrate using such an apparatus. The lateral homogeneity of the deposited layers is improved by one of several techniques.