Since the early 1990s digital X-ray detectors have been used extensively for medical imaging applications, such as Mammography, General Radiography, Computed Tomography, Tomosynthesis, Fluoroscopy, etc. The quality of a radiograph needs to be adequate to provide the required information for a given task. The primary physical parameters that affect image quality are spatial resolution, noise, and contrast. The Modulation Transfer Function (MTF) is the combination of contrast and resolution, the Noise Power Spectrum (NPS) combines the noise and resolution, and the Signal-to-Noise Ratio (SNR) expresses the ratio between signal and noise in large scale objects (i.e. at zero spatial frequency). The combination of SNR, MTF and NPS determines the Detective Quantum Efficiency (DQE) which represents the ability to visualize object details of a certain size and contrast. This study is using image simulation to estimate how the experimentally measured SNR, MTF and NPS of several digital X-ray detectors affect the mammographic image quality. The latter is measured in terms of Contrast-to-Noise Ratio (CNR) and Contrast-Detail (CD) analysis, using synthetic breast and CDMAM phantoms, respectively.