The Cherenkov radiation is often used for the particle identification (PID) not only in high energy physics experiments. Large area photon detectors have to be equipped making a strong constraint on the photon detector''s costs and in the mechanical realisation. The THick Gas Electron Multiplier (THGEM) is derived from the Gas Electron Multiplier (GEM) design, scaling the geometrical parameters and changing the production technology. The THGEM is a good candidate for the Cherenkov imaging applications because of good single photon detection efficiency, intrinsic mechanical stiffness and robustness against the electrical discharges. Other issues related to the efficiency of photon detection, e.g. the ion bombardment on the photocathode, are presented. The systematic studies here reported throw light also on the correlation between the THGEM performance as detector of ionising particles and the geometrical parameters related to the production process. The results discussed can be used not only for Cherenkov imaging applications.