Selective progesterone receptor modulator ulipristal acetate (UPA) is a drug used in management of symptomatic myomas. It was observed that the response to UPA treatment in uterine myomas varied amongst patients. An attempt was thus made at establishing predictive factors conducive to better reaction to treatment with UPA. The aim of this study was to assess the efficacy of UPA treatment in women with myomas, depending on pretreatment myomas' volume, number of myomas, age of patients, estrogenic status of women, and pretreatment blood flow in uterine arteries. The study included patients with one to four myomas. The UPA treatment was a preparation stage for surgical treatment in all patients. The study group was divided into the subgroups according to pretreatment myomas' volume, number of myomas, age of patients, estrogenic status of women, and pretreatment blood flow in uterine arteries. A better effect of reduction in size of myomas after UPA treatment was noted when pretreatment myomas' volume was lower than 30 cm3. A significant reduction in fibroids' size was observed after UPA therapy independently of the number of myomas and age of patients. A good response after the UPA therapy was observed when pretreatment estradiol concentration was below 50 pg/mL and when uterine artery resistance index (RI) was above 0.8. Our research demonstrates that treatment with ulipristal acetate is an efficient method in preoperative preparation of patients with uterine fibroids. The most important factor of positive response to UPA therapy is myoma volume. The number of myomas and patient's age do not interfere with effects of UPA therapy. Pretreatment estradiol concentration is significant, yet secondary for the effects of therapy. The UPA therapy has no impact on blood flow in the uterine arteries and no adverse influence on estradiol concentrations.