Gas/particle partitioning of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) compounds in the ambient atmosphere were investigated at three different sites (urban-industrial, urban and sub-urban) in Istanbul. Average gas and particle phase concentrations were measured as 133 fg m(-3) and 1605 fg m(-3), respectively. Gas phase concentrations of polychlorinated dibenzo-p-dioxin/furan (PCDD/F) compounds were determined to be 128 fg m(-3), 50 fg m(-3), 153 fg m(-3) during summer season and 204 fg m(-3), 164 fg m(-3), 154 fg m(-3) during winter season for the respective three sampling sites. Particle phase concentrations were determined to be 287 fg m(-3), 176 fg m(-3), 160 fg m(-3) during summer and 6586 fg m(-3), 2570 fg m(-3) and 1861 fg m(-3) during winter season for those three sampling sites. Chlorination level and molecular weight of congeners affected gas/particle partitioning of PCDD/F compounds. Gas phase percentages of 2,3,7,8-TCDD and OCDD concentrations were determined to be 47% and 1% respectively. A relatively high correlation was found between total particle matter (TPM) and particle phase PCDD/F concentration during winter season. (c) 2014 Elsevier Ltd. All rights reserved.