This paper analyses demographic ageing of the population in the County of Šibenik-Knin by using basic demographic indicators based on data collected from population censuses from 1971 to 2011. It analyses spatial differentiation of the ageing process at the level of the County, micro-regions, towns/municipalities and settlements. The research also provides a comparison of population ageing in different counties of the Republic of Croatia, from which it is evident that the County of Šibenik-Knin, as well as the Country of Lika-Senj, has the oldest population in Croatia. Ageing in the County of Šibenik-Knin, which was triggered by extreme rural exodus that was most intensive from the end of 1960s to the early 1970s, as well as by continuous declining fertility rates and by inherited age composition, was recorded at all territorial levels of the County. Although the ageing process started in littoral area (Primorje), hinterland (Zagora) experienced a faster and more intensive ageing. Based on numerous indicators of demographic ageing and its intensity, and compared with the point value indicators of ageing, it is evident that the population of the County of Šibenik-Knin is characterized by advanced old age. However, more than half of the observed settlements are characterized by very advanced or extremely advanced old age.