Aim: To analyse mothers' self-assessed quality of interaction with their children and their opinions about child difficulty with respect to socio-economic status and subjective factors: postnatal depression, social isolation, sense of coherence and locus of control. Methods and material: A comprehensive questionnaire was completed by 1039 mothers of 18-mo-old children participating in the baseline measurements of a Swedish multicentre study developing and testing a new psychosocial model for the child health services. Results: All subjective factors, including the number of factors, showed significant associations with perceived interaction and difficultness. Effect sizes of subjective factors ranged from about 0.3 to 1 SD for interaction, and from about 0.2 to 0.8 SD for difficultness. As for difficultness, effect sizes were larger for boys. There were no associations between high socio-economic status and high-quality interaction or low child difficultness: the few significant differences in fact favoured low-status children.