The present invention relates to a device (1) for fractional flow reserve determination, the device (1) comprising: a model source (10) configured to provide a first three-dimensional model (3DM1) of a portion of an imaged vascular vessel tree (VVT) surrounding a stenosed vessel segment (SVS) and configured to provide a second three-dimensional model (3DM2) of a pressure wire insertable into the vascular vessel tree (VVT); and a processor (20) configured to calculate a first blood flow (Q1) through the stenosed vessel segment (SVS) with the pressure wire (PW) inserted into the vascular vessel tree (VVT) based on the first and the second three-dimensional model and to calculate a second blood flow (Q2) through the stenosed vessel segment (SVS) without the pressure wire (PW) inserted into the vascular vessel tree (VVT) based on the first three-dimensional model (3DM1) and to determine a first fractional flow reserve value (FFR1) to be measured with the pressure wire (PW) inserted into the vascular vessel tree (VVT) based on the first blood flow (Q1) and to determine a second fractional flow reserve value (FFR2) to be measured without the pressure wire (PW) inserted into the vascular vessel tree (VVT) based on the second blood flow (Q1).