Premenstrual Dysphoric Disorder (PMDD) is characterized by cyclical mood changes resulting in clinically significant distress and functional impairment. Studies on momentary cognitive and affective states and their interplay during daily life over the menstrual cycle in affected women are still lacking. Using Ecological Momentary Assessment with electronic diaries, 61 women with current PMDD and 61 healthy control women reported their current mood, rumination, and self-acceptance eight times a day over two consecutive days per cycle phase (menstrual, follicular, ovulatory, and late luteal phase). Results revealed that women with PMDD showed significant increases in negative affect and rumination and decreases in positive affect and self-acceptance toward the end of the cycle. Lagged analyses demonstrated stronger within-person reciprocal effects of cognitions and mood in PMDD women compared to controls with the effect of rumination on subsequent negative affect being limited to the late luteal phase. Identified stronger prospective associations between cognitive processes and mood deteriorations in women with PMDD suggest that affected women are more sensitive to detrimental effects of either dimension. ... mehrHence, therapeutic strategies aiming at reducing ruminative thoughts and improving self-acceptance such as mindfulness-based interventions could be promising for reducing the burden of PMDD.