Imaging of blood flow with colour Doppler sonography is an established method in prenatal medicine. Today, there are several techniques which offer colour visualisation whose quality is on a par with that of the B-mode. One example of such a technique is Advanced Dynamic Flow (ADF). Looking at two cases, we will describe the clinical use of ADF to visualise fetal vascular tumours. The quality of blood flow imaging with ADF is similar to that achieved with conventional colour Doppler. Since ADF uses a different frequency range than colour Doppler the colour is not superimposed on the B-mode. This avoids blooming artefacts and provides good delineation. Particularly, the visualisation of periphery and neighbouring vessels is improved with ADF. The insonation angle is now of minor importance. However, ADF is not able to depict turbulence.