The interaction of molecular iodine with pristine and monovacant boron-nitride quantum dots (QDs) have been investigated using density functional theory. It was found that removing one B or N single atom significantly decreased the calculated E-g values at various exchange functional. In B-defected BN system, the localized spin densities canceled each other and overall polarization of system was found to be equal to unity. For N-defected system there was smaller spin densities localized on each closest B atoms. Both B-and N-vacancies caused appearance of new states in gap region. Our calculation revealed that spin density and polarization of defected system are localized on vacancy region and other atoms did not take part in this polarization. The results of electron localization function for N-DBN showed there was high density region at the position of removed nitrogen atom. The calculated adsorption energies implied that there was no significant chemical interaction between iodine molecule and pristine BN sheet. We suggested that when a deficiency was imposed to the BN sheet, the reactivity of the modified system toward iodine molecule significantly could increase. We found strong interaction between iodine and nitrogen atoms of B-DBN system. In the case of I-2/N-DBN system the neighbor atoms had no contribution in spin polarization of the system and it seemed that all spin density of system transferred to the iodine molecule after adsorption. Strong correlation between molecular iodine orientation and BN-QDs via their interactions type has been clarified in this work. These findings may provide a deeper insight into halogen molecules interactions with low dimensional defected boron nitrides. (C) 2017 Elsevier B.V. All rights reserved.