The steam reforming and oxidative steam reforming of dimethyl ether (DME) were tested at 573-773 K over a CuZn/ZrO2 catalyst in microreactors with three different types of channels: ceramic square channels with side lengths of 900 and 400 mu m, and silicon microchannels of 2 mu m of diameter. The channels were first coated with ZrOCl2 (ceramic channels) or Zr(i-PrO)(4) (silicon microchannels) and calcined at 773 K for 2 h to obtain a homogeneous and well-adhered ZrO2 layer, as determined by SEM, and then Cu and Zn (Cu: Zn= 1: 1 M, 20 wt% total metal) were co-impregnated. Operation at highly reduced residence time (10-3 s) while achieving hydrogen yields similar to those recorded over the ceramic channels was possible for the silicon microchannels due to the three orders of magnitude increased contact area. In addition, the amount of catalyst used for coating the silicon microchannels was two orders of magnitude lower with respect to the conventional ceramic channels. Outstanding specific hydrogen production rates of 0.9 L-N of H-2 per min and cm(3) of reactor volume were achieved as well as stable operation for 80 h, which demonstrates the feasibility of using on-site, on-demand hydrogen generation from DME for portable fuel cell applications.