The reactions of the halide anions (F-, Cl-, Br-, and I-), NO2-, SF6-, CO3- and CO4- with ClONO2 have been studied at room temperature in a flowing afterglow apparatus. All these reactions are found to proceed at the collision limit and the experimental data are compared with literature values. The reaction of I- with ClONO2 was studied at stratospheric pressures and temperatures in view of its use as a possible precursor ion for the measurement of stratospheric N2O5+ClONO2 mixing ratio height profiles by chemical ionization mass spectrometry. No pressure or temperature dependence of the rate constant has been observed. In order to correct the observed rate constants for HNO3 impurities, the reaction rate constants of F-, Br-, and NO2- with HNO3 have also been determined. In addition, the apparent second-order clustering rate constant of NO3- with ClONO2 in Ar/N2 and Ar/He mixtures has been measured.