The specialized software intended for active thermal nondestructive testing (NDT) is developed. The software is oriented toward both commercial and laboratory thermal NDT systems including heat sources and infrared imagers of various types. A modeling module is an essential part of this software allowing optimization of test procedures. Experimental data is treated by using a processing and defect characterization modules intended for enhancing signal-to-noise ratio and identifying lateral size, depth and thermal resistance of hidden defects. Keywords: thermal NDT, modeling, defect characterization.