Objective: Several researches investigated the attitudes of heterosexuals and LGBT people towards marriage and parenting of lesbians and gays. The objective of the present study is to explore the correlation between these attitudes and levels of sexism, social homophobia and internalized sexual stigma. Design and Method: The participants were 826 (534 F, 292 M), aged between 17 and 70. 59,8% defined him/her-self as “exclusively heterosexual”, 29,2% as “exclusively homosexual” and 11% as “bisexual”. The following tests have been administered: Questionnaire on socio-demographic Information, Ambivalent Sexism Inventory; Measure of Internalized Sexual Stigma for Lesbians and Gays; Modern Homophobia Scale, The Katuzny Same-sex Marriage Scale; D’Amore and Green Same-sex Parenting Scale. Results: Positive correlations have been found between: sexism and homophobia (r = .378; p < .01) and sexism and internalized sexual stigma (r = .320; p < .01). Male subjects obtained higher scores in sexism (F(1,559) = 15,555; p < .01) and homophobia (F(1,559) = 44,977; p < .01). Heterosexuals were significantly less favorable regarding gay and lesbian marriage (F(1,821) = 96,936; p < .05) and parenthood (F(1,821) = 84,260; p < .05) compared to the non-heterosexuals. Heterosexual males were the most unfavorable towards parenting (F(1,821) = 4,786; p < .05). Conclusions: The results offer a contribution to scientific research which still has significant gaps regarding the attitude-associated variables towards marriage and parenting of people of the same gender. Sexual education at schools and clinic supervision interventions should take these evidences into account.