This research links residence with biological and nonbiological married and unmarried parents to the cognitive achievement and behavioral problems of children aged 3–12, controlling for factors that make such families different. The data were drawn from the 1997 Child Development Supplement to the Panel Study of Income Dynamics. Achievement differences were not associated with father family structure per se, but with demographic and economic factors that differ across families. In contrast, behavioral problems were linked to family structure even after controls for measured and unmeasured factors were included. Children in all family types except the married-biological-parent family showed higher levels of behavioral problems. Paternal and maternal engagement time explained some of the differences in behavioral problems across families. Although children in blended families tended to achieve at lower levels than those not in blended families, stepchildren in blended families achieved at levels comparable to those of half-siblings. Finally, children in blended families tended to have fewer behavioral problems than those not in blended families.