BACKGROUND: Adult-children caring for a parent with cancer comprise a significant segment of caregivers. Yet less is known about adult-child caregivers, their burden, or caregivers' and patients' gender's impact, which may differ from the well-studied spousal caregiver. This knowledge gap may hinder efforts to ameliorate adult-children's caregiver burden. METHODS: We analyzed caregiver surveys from the Cancer Care Outcomes Research and Surveillance Consortium, a multi-regional population-based study of patients with colorectal or lung cancer. Using t tests and multivariate regression models, we assessed whether adult-child and spousal caregivers' caregiving responsibilities and social/emotional and financial burdens differed and used structural equation models (SEMs) to examine mediating factors. RESULTS: Compared with spouses/partners (N = 1007), adult-children (N = 227) spent less time caregiving (14 vs 23 hours/week; P < .001), but experienced higher social/ emotional burden (P < .01). In models adjusted for objective caregiving burden measures and demographics, adult-children's social/emotional (P < .05) and financial burdens (P < .01) were greater than spouses'. Poor communication quality was associated with greater social/emotional burden for both groups (P < .05). SEMs indicated that gender concordance between caregivers and patients (eg, daughters caring for mothers) and caregiver employment increased the difference between adult-child and spouses' social/emotional burden, whereas caregiver-patient relationship quality reduced it. CONCLUSIONS: Adult-children spend less time caregiving than spouses/partners, but have higher social/emotional and financial caregiving burdens, partially due to adult-children's employment, caregiver-patients' gender concordance, and relationship quality. Gender concordance's contribution to greater social/emotional burden adds important context to prior findings, indicating female caregivers experience the most burden. Interventions that improve caregiver-patient communication may reduce both adult-child and spousal caregiver burden.