This thesis investigates the influence of background profiles and neutrals on scrape-off layer (SOL) filaments in fusion devices using 3D simulations. This was achieved by seeding filaments on steady-state background profiles including neutrals. In terms of the filament motion, both direct and indirect interaction between the neutrals and filaments have been studied. The simulations have been carried out using the STORM module, which is implemented using the BOUT++ library. STORM has been extended to include neutrals, using a new neutrals C++-API which also uses BOUT++. Filaments have been seeded on top of plasma backgrounds with changing plasma density and temperatures. The profiles have been generated by running a reduced set of equations to steady state. The backgrounds cover different regimes, namely low-recycling regime, high recycling as well as detached plasma conditions. In the attached conditions, the filament’s radial velocity increased with increasing target temperature, suggesting that sheath currents and plasma viscosity significantly influence the studied filaments. Interaction with the neutrals reduced the filament’s radial velocity, especially in the high tem- perature and high density conditions. As detachment was reached, the filament’s velocity increased temporar- ily, as sheath currents were strongly suppressed by the high resistivity, caused by a highly dense, cold plasma in front of the target, before the general decreasing trend is recovered for higher densities. In detached con- ditions the neutrals had an increased impact on the filament dynamics, and partially replaced sheath currents by friction in the detachment front.