Threshold contrast visibility measurements are used in mammography to assess image quality. The CDMAM contrast detail phantom version 3.4 was used to set the European standards for quality assurance in digital mammography. As such, the phantom has been widely used to assess the threshold contrast of clinical mammography equipment across Ireland. Recently an updated version of the phantom, version 4.0, was released. The CDMAM 4.0 consists of a new layout with more disc diameters and thicknesses than its predecessor. The new version was created with the aim to be more closely adopted to the image quality found in modern mammography systems and to reduce the variability across individual phantoms. This study compares the sensitivity of the two versions of the CDMAM phantom across a range of mammography systems at clinical settings. Contrast detail measurements were taken using the different phantoms on four different makes of digital mammography equipment and images were analysed using CDMAM Analysis v2.1.0 software package. Here we present resuts of a comparison in threshold contrast sensitivity between the two versions of the phantom.