Some observations of recombination radio lines (RRL) of carbon from photo dissociation regions (PDR) at millimetre wavelengths were carried out. Combination of the RRL data with observations of the same objects in IR fine-structure lines of carbon (C II) and oxygen (O I) allows one to determine physical conditions in the PDR (density, temperature, region thickness), that was performed for a number of PDR related with H II regions. Is shown that RRLs allow also to investigate the kinematics of a complex of PDR — H II region.