The invention relates to a modular plasma jet treatment system (1), particularly for therapeutic or oral applications, comprising a plasma source (2) with least the following components; a high-voltage module (20) comprising a high-voltage electrode (21) and first connection means, a plasma jet applicator (30) configured to generate at least one plasma jet (35), wherein the plasma jet applicator (30) comprises a cavity (31) for a process gas (100), wherein a ceiling portion (32) of the cavity (31) is either arranged on the plasma jet applicator (30) and/or on the high-voltage module (20), the cavity (31) comprising a process gas inlet (33) and at least one plasma jet outlet (34), wherein the plasma jet applicator (30) comprises a second connection means, wherein the first and second connection means are configured such that the plasma jet applicator (30) and the high-voltage module (20) are repeatedly connectable and releasable, wherein, when the plasma jet applicator (30) is connected to the high-voltage module (20), the cavity (31) is adjacently arranged with the ceiling portion (32) at the high-voltage module (20), and wherein the cavity (31) is separated by a dielectric (23, 47) from the high-voltage electrode (21) of the high-voltage module (20).