Transition metal dichalcogenide (TMD) monolayers (ML) on a substrate are very promising for optoelectronic application because they have direct band gap in visible range than can be easily tuned by variation of composition: for example, MoxW(1-x)S2ySe2(1-y) compounds can be tuned continuously in the range of 2.1-1.5 eV. Increasing the thickness up to 3 ML extends the range of tunability down to 1 eV. Optical techniques are widely used for characterization of TMDs, starting from simple visualization to crystallographic symmetry and structural characterization by second harmonic generation microscopy (SHGM) and band structural and excitonic characterization by photoluminescence microscopy (PLM)-spectroscopy. Femtosecond optical pump probe technique gives information about excitation and relaxation of charge carriers, which is related to a carriers’ mobility. Here we present the results of the optical studies of 2D TMDs by SHGM, PLM and femtosecond optical pump-probe technique, which studies were complemented by atomic force microscopy (AFM). Optical experiments were carried out at wavelength of 800 nm or 400 nm and pulse width of 100 fs in confocal geometry. The material studied were MoS2, WS2, MoSe2, WSe2 and their solid solutions with the thickness of 1 ML – 3 ML fabricated by chemical vapor deposition and exfoliation techniques. Quality of the exfoliated flakes was confirmed by PLM in the flakes as thick as from one to 5 ML. SHGM revealed the presence of edge effects due to halogen molecules intercalated between single monolayers, which results in strong decrease on increase of second harmonic intensity. For chemically deposited films, their quality depend strongly on the parameters of deposition: even when SHGM shows single crystallinity, low intensity of PLM points to high defects concentration, which results in luminescence quenching. In the pump probe experiments, only WSe2 is sensitive for the used probing wavelength of 800 nm, because the energy of this pulse of 1.55 eV falls into the edge of absorption band. Experimentally, two time constants (of about 1 ps and > 50 ps) were found in the relaxation process. Theoretically, the relaxation process was described in the frame of the model taking into account the energy exchange between thermalized carriers and dispersionless longitudinal optical phonons; good agreement with the experimental results was achived.