The aim of the study was to determine which vasoactive agent was more efficacious for erectile dysfunction (ED), intracavernosal papaverine or oral sildenafil, in paraplegic men within the first year after injury by using a penile color Doppler ultrasound as a quantitative imaging method and to determine the association between responses to these two vasoactive agents and factors such as neurological lesion level and lesion severity. A total of 31 male in-patients with spinal cord injury, aged over 18 years, and with neurological lesions below the T6 level within the first year after injury with ED were included. Visual and auditory sexual stimulus (VASS) on day 1 (group 1), VASS with 25 mg intracavernosal papaverine (group 2) and after a wash-out period of papaverine on day 2, and VASS with 50 mg oral sildenafil on day 5 (group 3) were administered to each patient. Measurements of the peak systolic velocity and end diastolic velocity, which were used as vascular parameters during each procedure type, were taken using penile color Doppler ultrasound. Considering the severity of the lesion and the levels of the neurological lesion, there was a statistically significant difference between the PSV values of the group 1 and the other two groups (P less than 0.05). There was no statistically significant difference between the peak systolic velocity and end diastolic velocity values of groups 2 and 3 (P greater than 0.05) in terms of both the severity and the levels of the lesion. Efficacies of intracavernosal papaverine hydrochloride or oral sildenafil citrate for ED were similar at all neurological lesion levels and lesion severity in paraplegic men within the first year after spinal cord injury.