While factors influencing maternal emotional availability (EA) have been well investigated, little is known about the development of child EA. The present longitudinal study investigated the role of frontal brain asymmetry in young children with regard to child EA (child responsiveness and involvement) in mother-child interaction in a sample of 28 children at 7, 14, and 50 months of age. When infants were 7 months of age, mother-child interaction quality was assessed using the EA-Scales. At 14 months, infants' resting asymmetric frontal activity was assessed by means of the electroencephalogram (EEG). When children were 50 months old, mother-child interaction quality was measured again. Analyses showed that relatively higher left frontal EEG activation was related to higher child involvement at 50 months, but not to child responsiveness. Those findings suggest a specific relation between individual differences in frontal asymmetry, and child approach and initiating behaviors in mother-child interaction.