Construct validity of the newly developed Preschool Assessment of Attachment (PAA) was examined in a sample of depressed and nondepressed mothers and their preschoolers, focusing on attachment related differences in children's general caregiving environments, maternal psychosocial functioning, and child behavior during interactions with mother. Mothers of secure children were more emotionally and verbally responsive to their children than were mothers of insecure children, and secure children were emotionally more positive to their mothers than were insecure children. Mothers of secure children also reported higher levels of social supports than did mothers of insecure children. Finally, dyads with children who lacked unitary, coherent attachment strategies (i.e., anxious depressed, defended/coercive, and insecure other) showed the worst functioning in all domains relative to all other attachment groups. Similar but slightly less robust findings were obtained with socioeconomic variables statistically controlled. These results lend support to the PAA as a valid system for the conceptualization and measurement of quality of attachment among preschoolers. Future research applications with the PAA are discussed.