A computational study of fluid-structure interactions in deformable microchannels with a single compliant top wall is presented here. Several theoretical models [2-4] were tested against full three-dimensional two-way-coupled fluid-structure interaction simulations. Three types of microchannels, which have been experimentally characterized previously and represent different elasticity regimes, were chosen as benchmarks for theory and simulations. Furthermore, an extension to the theoretical analysis in [4] was made to include thick compliant walls. Good agreement was found in most cases for the predicted, simulated and measured flow rate-pressure drop relationships. The deformation prole of the top wall of the microchannel in any flow-wise cross section predicted by simulations also showed good agreement with the theory. Specically, the prediction that the span-wise displacement in a long shallow microchannel decouples from the flow-wise deformation was confirmed, and the predicted scaling of the maximum displacement with the hydrodynamic pressure was validated.