Young mothers often look for solutions to problems related to childcare in groups associating other mothers on Facebook. One can find there not only numerous advice on, among others, nutrition, care or even treatment of infants, but also learn about various consumer trends. The aim of the article is to determine the role of social proof on groups of young mothers on Facebook in making consumer decisions. The research method used was the content analysis on a selected Polish group for young mothers on Facebook. It was hypothesized that social proof on Facebook groups is important in making consumer decisions of young mothers regarding their children. This applies to all products intended for young children, from care products, food products, toys, accessories for children, to medicinal products. Young mothers are often influenced by the prevailing trends and opinions of other members of the group for young mothers, who may be real mothers or – which one may not be aware of - representatives of various brands.