A 42 years old woman suffering from repeated events of intensive vaginal bleeding during the week off birth control pills was referred for diagnostic hysteroscopy. The patient underwent hysterohy drosonoscopy, a 3-step procedure, including a transvaginal ultrasound scan, a diagnostic hysteroscopy and immediate hydrosonography. A3 cmintramural myoma was detected by the ultrasound scan without impinging onto the uterine cavity as visualized by diagnostic hysteroscopy. However, continuous hydrosonographic evaluation of the uterus, performed immediately afterwards, unveiled a fibroid with a significant intracavitary portion. A falsely normal cavity could be appreciated by high pressured hysteroscopy, while during the gradual fall of the intracavitary pressure a significant lesion could be revealed encroaching into the lumen. In the absence of an agreed distention pressure range during hysteroscopy, an immediate hydrosonography may serve as an auxiliary tool to follow the uterine wall contour as distention pressure declines during the eventual escape of the distention fluid from the lumen. Uterine wall contour is heavily dependent on the distension pressure and guidelines for intrcavitary pressure during hysteroscopy are evidently needed.