Penile prosthesis is the treatment of choice for erectile dysfunction (ED) refractory to medical treatment; vasculogenic ED and ED postradical prostatectomy (PRP) are the main aetiologies. Few studies have compared surgical outcomes of penile prosthesis placement for vasculogenic versus PRP severe erectile dysfunction. This study includes 117 cases corresponding to virgin implants for ED of either vasculogenic aetiology or PRP (58 for PRP and 59 for vasculogenic cases). We analysed data corresponding to: age, comorbidity, type of prosthesis, presence of fibrosis that hinders dilation, need for modelling, size of implanted cylinders and complications (intra and postoperative). In the results the rate of hypertension, diabetes, dyslipidaemia and ischemic heart disease was higher in vasculogenic ED. All of the prostheses were hydraulic; 24.1% of two components and 75.9% of three in the PRP group; 39% components of two and 61% of three in the vasculogenic group. With regard to the presence of cavernous fibrosis and need for modelling, no significant differences were found. However, significant differences were observed in the size of the implanted cylinders; PRP of 18.30 ± 2.11 cm versus 19.21 ± 1.71 cm in vasculogenic ED (p = 0.01643). There were no significant differences between the groups in infection rates, mechanical failure or extrusion. In conclusion the implantation of penile prosthesis in ED after PRP is associated with a shorter cylinder length compared with vasculogenic origin. Although there was a certain non-significant tendency to the need for modelling manoeuvres in PRP, there were no significant differences in postoperative outcomes including infection or mechanical failure.