Children's fatness has become a central concern worldwide, Finland included. In Finland, fatness is mainly discussed from the biomedical viewpoint as a considerable health risk resulting from individual ways of life. In the case of childhood fatness, it is the parents that are mainly held responsible for its prevention and treatment. It has been widely noted that fat people are often blamed for such things as laziness and lack of self-control. As regards fat children, however, the role and possible blaming of parents has received less scholarly attention. This paper examines the ways children's fatness is explained in an anonymous Finnish Internet discussion, focusing especially on the ways parents are depicted as causing their child's fatness and as possibly blameworthy for this. A discourse analysis revealed that parents were mainly viewed as the primary cause of the child's fatness and were negatively constructed as having 'lousy' characters, being unable to create an 'adequate' emotional bond with their child, or as otherwise engaging in 'faulty' child-rearing practices. Significantly, the latter two constructions included notions similar to the psychological expert notions of parenthood. All three constructions of parents were also gendered, being either implicitly or explicitly equated with the mother. Children's fatness was also explained, and parents' primary role thus questioned or mitigated, by reference to some other factors, such as genes. These explanations, however, did not seem to hold their ground in the discussion. The occurrence and implications of these explanations is discussed.