A 0.05 km2 patterned bog and a 0.29 km2 ribbed fen were compared to determine the influence of their morphometry on runoff and evapotranspiration. The bog hydrology was dominated by irregularly located and poorly linked pools ≤1.0 m deep, separated by prominent ridges containing local water-table maxima. This small basin had an appreciable lag-to-peak time (e.g. 6 h), and a low runoff ratio (0.1 to 0.2), because of the large depression storage of the pools, and a long detention storage caused by the weak pool-to-pool linkage. The ribbed fen was dominated by a 1.3 km water track, which consisted of shallow pools (≤0.25 m deep), separated by low ridges that did not produce local water table maxima. The pools were well linked, but their sequential arrangement resulted in a very large detention storage which trimmed the runoff ratio to only 0.003 to 0.07. The lag-to-peak time was relatively short (approx. 3 h), because of sheet flow in the lower water track, just above the weir. The large depression and detention storage of both systems enhanced evapotranspiration losses. Between July 5 and August 14, 1990, evapotranspiration from the bog was 97 mm, compared to 126 mm from the fen, while runoff was only 12 and 28 mm for the bog and fen, respectively. Evapotranspiration from ridges was 67 and 84% of pool evaporation, in the bog and fen respectively.