Tourism demand, as a set of goods and services people consume during their travels, greatly affects tourism development in a destination. Hence, forecasting tourism demand is the subject of numerous studies in the field of tourism. Many of these studies use a time series analysis approach to examine tourism demand, foremost through tourist arrivals but also through the number of overnights and tourist expenditure. The purpose of this paper is twofold: to examine trends in tourist arrivals in the city of Rijeka, Croatia over the last ten-year period and to forecast tourist arrivals in the near future. The time series analysis method is applied to this end, with tourism demand being measured by the overall number of tourist arrivals. The research findings provide deeper insights into, and a better understanding of, tourism demand forecasting as a factor of efficient tourism planning.