Laser, operating in the range of 1-2 μm (NIR), is currently an attractive candidate for various applications include ranging, 3D scanning laser radar, communication and other areas where human contact with the laser radiation is possible. The present work is focused on application of PbSe or PbSe/PbS semiconductor nanometer-sized crystals (NCs) for passive Q-switching of NIR laser. Owing to narrow band gap and large exciton Bohr radius of the bulk materials, the NCs of PbSe and PbS acquire unique properties: The quantization effects are strongly pronounced in PbSe and PbS NCs, the strong quantum confinement is thus easily obtained, and the ground-state absorption edge can be tuned over a wide wavelength range (from the visible to infrared). The NCs gain properties of saturable absorber, which allow using them as optical switches. We propose a colloidal synthesis procedure for the preparation of size-selected NCs, suitable for Q-switching of NIR laser. Colloidal synthesis allows simple control over the size of the crystals, and therefore, provides a possibility to produce the samples with desired absorption band position. This method is also very effective for stabilization of NCs and a passivation of their surface with the help of organic ligands.