Gas-liquid interfacial atmospheric-pressure plasma jets (GLI-APPJ) are used medically for plasma-induced cell-membrane permeabilization. In an attempt to identify the dominant factors induced by GLI-APPJ responsible for enhancing cell-membrane permeability, the concentration and distribution of plasma-produced reactive species in the gas and liquid phase regions are measured. These reactive species are classified in terms of their life-span: long-lived (e.g., H₂O₂), short-lived (e.g., O₂^•−), and extremely-short-lived (e.g., ^•OH). The concentration of plasma-produced ^•OH_aq in the liquid phase region decreases with an increase in solution thickness ( •OH_aq, resulting from the center-peaked distribution of ^•OH in the gas phase region, corresponds with the distribution of the permeabilized cells upon APPJ irradiation, whereas the overall plasma-produced oxidizing species such as H₂O_2aq in solution exhibit a doughnut-shaped horizontal distribution. These results suggest that ^•OH_aq is likely one of the dominant factors responsible for plasma-induced cell-membrane permeabilization.