One of the possible ways to increase sensitivity of ion mobility spectrometers for explosives detection is the use of dopants - substances enhancing ion formation. The specificity of laser ionization in ion mobility spectrometry with regard to possible dopants - ion-formation enhancers - remains still unclear when detecting nitro compounds. The purpose of this work was to study the opportunities to increase sensitivity of detection of explosives at the presence of dopants under laser ionization of sample vapors. Trinitrotoluene (TNT) was used as an explosive. Toluene, naphthalene and chloroform were chosen as dopants, as they differ in the magnitude of ionization potential and in the value of electron affinity. The laser radiation had a wavelength of λ=266 nm and a repetition rate of 10 Hz. It was found that the use of toluene at laser intensities (0.04÷3).107 W/cm2 leads to an increase of TNT ion signal by 50%. The use of naphthalene leads to an increase of TNT ion signal by 15%. It was found that chloroform reduces the efficiency of formation of negative ions of TNT due to the capture of free electrons. This is caused by its high electron affinity and the impossibility of two-step ionization mechanism of chloroform for the laser intensities used.