Advanced parental age might constitute a risk factor for various disorders. We tested whether this concerns also mood disorder patients. The study included 314 subjects (42 bipolar-BD patients; 21 manics and 21 depressives, 68 unipolar-UD, and 204 normal controls-NC). Analysis of Covariance (ANCOVA) and the calculation of the Relative Risk (RR) and the Odds Ratio (OR) were used for the analysis. Paternal age differed between NC and UD patients (29.42 ± 6.07 vs. 32.12 ± 5.54;  = .01) and manics (29.42 ± 6.07 vs. 35.00 ± 5.75;  = .001) and maternal age between NC and manics (25.46 ± 4.52 vs. 31.43 ± 4.75;  < .001) and manic and UD (31.43 ± 4.75 vs. 26.75 ± 6.03;  = .002). The RR and OR values suggested that advanced parental age constitutes a risk factor for the development of mood disorders. In a non-dose dependent and gender-independent, advanced parental age constitutes a risk factor for the development of BD with index episode of mania (probably manic predominant polarity); only advanced paternal age constitutes a risk factor for the development of UD and BD with index episode of depression (probably depressive predominant polarity). This is the first study suggesting differential effect of advanced parental age depending on predominant polarity of BD.