Cancrinite crystals possessing parallel nanochannels are attractive for incorporation of guest materials and preparation of one-dimensional structures. In this work, we study variety of cancrinite crystals synthesized with Se inside their channels. Single crystal x-ray diffraction, polarized Raman, optical absorption, and luminescence spectra are investigated. It is shown that Se is stabilized in the form of Se-2(2-) and Se-2(-) dimers located in the center of the channel and oriented along the channel. Different absolute and relative concentrations of Se-2(2-) and Se-2(-) are obtained for different samples. The Se-2(2-) dimers at high concentration show tendency to organize linear chains. At low temperatures, quite strong interdimer bonding for both Se-2(2-) and Se-2(-) is observed. Another important low-temperature effect is appearance of additional Raman bands, which are attributed to the vibrations of linear Se-2(2-) chains distorted by the incommensurate potential of cancrinite. Strong near-infrared polarized luminescence is observed for all samples. Photoionization of dimers is shown to be important step in the mechanism of the luminescence.