Identification of hereditary predisposition to cancer has limited significance if not followed by efficient cancer prevention. The responsibility of informing offspring about genetic risk often falls to the parents. We systematically investigated how parents with Lynch Syndrome share knowledge of genetic risk with their offspring, challenges in the communication process and wish for professional support. Of all known mutation carriers over age 40 (n = 337) in 102 Finnish Lynch Syndrome families, 86% completed a self-reported questionnaire; 248 of them (86%) had children. Of the 248 parents, 87% reported disclosure and 13% nondisclosure. Reasons for nondisclosure were mainly the young age of offspring, socially distant relationships, or feeling of difficulty in discussing the topic. Men reported significantly more often disclosure with a support person (spouse etc.) (P < 0.001). The most difficult communication aspect was discussing children's cancer risk. Of the 191 firstborn adult children informed, 69% had taken the predictive genetic test. Every third parent suggested that health professionals should be involved in passing on the information and that a family appointment at the genetic clinic should be organized at the time of disclosure. Nearly all parents had informed their adult offspring about the genetic risk and possibility of genetic testing, but almost one-third were unsure of how their offspring had used the information. The challenge is to improve the communication processes, so that all offspring would get the information important for their health care, and parents would get the professional support desired at disclosure.