  A novel Positron Emission Tomography system, based on plastic scintillators,
is being developed by the J-PET collaboration. In this article we present the
simulation results of the scatter fraction, representing one of the parameters
crucial for background studies defined in the NEMA-NU-2-2012 norm. We elaborate
an event selection methods allowing to suppress events in which gamma quanta
were scattered in the phantom or underwent the multiple scattering in the
detector. The estimated scatter fraction for the single-layer J-PET scanner
varies from 37% to 53% depending on the applied energy threshold.
