STUDY QUESTION: What are the characteristics, motivations and expectations of men and women who search for a co-parent online? SUMMARY ANSWER: Male and female prospective co-parents differed in terms of their motivations, choice of co-parent and expectations of co-parenting, while differences according to sexual orientation were less marked. WHAT IS KNOWN ALREADY: Very few studies have addressed the experiences of elective co-parents, i.e. men and women who are not in a relationship with each other creating and raising a child together. No study has examined the motivations and experiences of those who seek co-parents online. STUDY DESIGN, SIZE AND DURATION: An online survey was completed by 102 participants (61 men, 41 women) who were members of Pride Angel, an online connection website that facilitates contact between people looking for someone with whom to have a child. The survey was live for 7 weeks. PARTICIPANTS/MATERIALS, SETTING, METHODS: Details of the survey were emailed to all members of Pride Angel. The survey obtained data on participants' demographic characteristics, motivations, choice of co-parent and expectations of co-parenting. Data were analysed to examine differences by gender and by sexual orientation within each gender. MAIN RESULTS AND THE ROLE OF CHANCE: Approximately one-third of men and one half of women seeking co-parenting arrangements were heterosexual. The majority (69, 68%) of participants were single, although significantly more gay and bisexual men (15, 36%) and lesbian and bisexual women (11, 55%) had a partner compared with heterosexual men (4, 20%) and heterosexual women (2, 12%), respectively. Overall, the most important motivation for seeking co-parenting arrangements was in order for both biological parents to be involved in the child's upbringing. Co-parents were looking for someone with a good medical history. Most female co-parents expected the child to live with them, whereas male co-parents either wished the child to reside with the mother or to live equally in both households. A higher proportion of gay and bisexual men than heterosexual men wanted daily contact with the child. LIMITATIONS, REASONS FOR CAUTION: Although this study presents data from the largest sample of elective co-parents to date, the main limitations were the low response rate and that only members of one website were approached. The findings may not be representative of all potential elective co-parents. WIDER IMPLICATIONS OF THE FINDINGS: This study provides important insights into the new phenomenon of elective co-parenting. With the increasing use of assisted reproductive technologies and the diversification of family forms, a growing number of people are seeking co-parenting arrangements to have children. While up until now, elective co-parenting has been principally associated with the gay and lesbian community, this study shows that, with the rise of co-parenting websites, increasing numbers of heterosexual men and women are seeking these types of parenting arrangements. This study generates the first findings on the expectations and motivations of those who seek co-parents online and examines whether these differ according to gender and sexual orientation. Future studies are needed to assess the impact of this new form of parenting on all involved, particularly the children. STUDY FUNDING/COMPETING INTERESTS: This study was supported by the Wellcome Trust (097857/Z/11/Z). Erika Tranfield is the co-founder of the website Pride Angel, the remaining authors have no conflicts of interest to declare.