Spin-polarized density functional theory calculations have been performed on armchair graphene quantum dots and boron-nitride quantum dots (AG/BNQDs) and the effect of carbon/boron-nitride sub-stitution on the electronic properties of these AG/BNQDs has been investigated. As a first step to consider more realistic quantum dots, quantum dots which are a combination of zigzag QDs and armchair QDs have been considered. Effect of substitution on these hybrid quantum dots has been explored for both GQDs and BNQDs and such results have been compared and contrasted with the results of substituted AG/BNQDs and their zigzag analogs. Our work suggests that the edge substitution can play an important tool while tuning the electronic properties of quantum dots. (C) 2014 Elsevier B. V. All rights reserved.