The potential of heat-exchange reactors with mm-scale channels to provide process intensification for homogeneously catalysed gas-liquid reactions was explored. The solvent-free hydroformylation of cyclododecatriene using a homogeneous catalyst was carried out in a heat-exchange (HEx) reactor with min-scale thin channels, and in a stirred batch autoclave for comparative purposes. The reaction was carried out using generally a concentration of 0.3 mol% catalyst from 50-85 degrees C temperatures and between 12 and 40 bar pressure. This channel flow is expected to provide increases in mass transfer while high heat transfer capability will accommodate the increased heat transfer duty resulting from increased reaction rates and the absence of the solvent. A simple kinetic model of the data obtained using both reactor types is derived allowing a comparison based on apparent turn-over frequencies. Operation in the HEx reactor was free of mass transfer limitations and the observed turnover frequency was independent of catalyst concentration. By contrast the catalyst productivity in the autoclave was a function of its concentration indicating mass transfer limitations. The observed reaction rate, in terms of apparent turnover frequency was 10-15 times higher in the heat-exchange reactor than the laboratory scale stirred tank. The selectivity to the desired monoaldehyde product was also higher in the HEx reactor. The temperature, pressure and catalyst concentration appear to have little influence of reaction selectivity (for the monoaldehyde) and the product distribution, this being dependent only on the concentration of cyclododecatriene and monoaldehyde. The reasons for this behaviour are discussed in detail. (C) 2007 Published by Elsevier B.V..