Background. The purpose of this study was to perform an ultrasonographic comparison of tension-free vaginal tape (TVT) and the TVT-obturator (TVT-O) procedure in women with stress urinary incontinence (SUI). Methods. We retrospectively reviewed 159 women with SUI undergoing either TVT (n = 91) or TVT-O (n = 68). All subjects underwent perineal ultrasonographies, pelvic examination, urinalyses, 1-h pad tests, multichannel urodynamic studies and a personal interview using the Bristol Female Lower Urinary Tract Symptoms Questionnaire before and 1 year after surgery. Results. At rest or during Valsalva, the middle of the TVT-O tape localised more distally than the TVT on ultrasound (p<0.01). A higher rate of urethral kinking during straining was observed in the TVT group compared with the TVT-O group after surgery (86.9 versus 23.9%, p<0.01). Mean operative time was significantly shorter in the TVT-O group (16.2 versus 28.6 min, p<0.01). The rate of objective cure was comparable for the TVT and TVT-O groups (94.5 versus 88.2%, p<0.05). However, subjective cure rate was significantly lower for the TVT-O than the TVT group (82.4 versus 93.4%, p = 0.042). There was no statistical difference between the 2 groups regarding patient characteristics and complication rates. Conclusions. TVT-O tape results in a less acute angle and localises to a more distal part of the urethra, resulting in less urethral compression and a lower rate of urethral dynamic kinking.