Chemical vapor deposition of the (111)- and (100)-oriented single-crystalline diamond films is studied by combining a reactor-scale model with an atomic-scale model. The reactor-scale model is based on the solution of a continuum fluid-flow/heat-transfer boundary value problem for a reactive gas in contact with a deposition surface. The atomic-scale modeling is carried out using a kinetic Monte Carlo method. A consistency between the two modeling schemes is achieved by: (a) using the reactor-scale modeling predictions as input to the atomic-scale modeling scheme and; (b) using the atomic-scale modeling results to identify the surface reactions which govern and, hence, should be used in reactor-scale modeling of the deposition of (111)- and (100)-oriented diamond films. It is found that by properly combining the two types of models, consistent predictions for the film deposition rates can be obtained over a relatively large range of the CVD processing conditions. In addition, different phenomena are found to govern the deposition process for (111)- and (100)-oriented films. In the case of (111)-oriented films, the film growth rate appears to be controlled by the nucleation of new layers. Contrary in the case of (100)-oriented films, both the nucleation and growth processes seem to have comparable effects.