Abstract: A positioning assembly for securing top box of window blinds or shades includes a positioning member which includes multiple hooking members, guide posts and two guide members. An adjustment member includes multiple lugs extending from a top thereof and each lug has an insertion hole. An extension splits from the adjusting member so as to insert into the slot of the positioning member. An engaging portion extends from a bottom of the adjustment member. Multiple springs are mounted to the guide posts and biased between the lugs and the guide posts which are inserted into the insertion holes of the lugs. The top box having an open side which is defined between a first lip and a second lip, wherein the first lip is hooked to one of the hooking members and the second lip is engaged with the engaging portion of the adjustment member.