Present report is concentrated on large-scale "quiet" structures of solar radioemission at millimetre wavelengths, especially, on regions of coronal holes. Our observations have been obtained with radio telescope RT-7.5 of Moscow Technical University at 3.4 mm wavelength with angular resolution about 2.5 arcmin. Since 1987 we have long sets of regular solar mapping. These maps allowed us to find out many dark regions (brightness depressions) on it, which have high correlation with X-ray dark regions as well as with EUV-spectral lines depressions (coronal holes) seen on solar images from Yohkoh, Coronas and SOHO. It is widely believed from radio observations in dm and cm domains that coronal-hole-associated depressions become indistinguishable at short wavelengths. But analysis of our observations shows definitely that in many cases at short mm wavelengths there are coronal-hole-associated darkenings on the disc and they are similar to X-ray and EUV images. The reasons of discrepancy between observations in cm and mm ranges are discussed: at long wavelengths coronal holes emission is observed but at short wavelengths under coronal hole chromosphere emission is observed.