Using the PION ICRH modelling code on JET tokamak pulses, the effect of including pitch angle dependence within the RF diffusion operator is investigated. This is found to be of greatest importance to the particle distribution function in cases of higher harmonic heating and lower heating ion mass, resulting in faster drop-off of the distribution’s tail and non-linear alterations to ion species power partition. ITER scenario operational parameters are also considered, and the same effect is found to be of relevance to ITER ICRF modelling needs.