This article presents an analysis of the issue surrounding the debts of the city of Vilnius in the 18th century, focusing mainly on the second half of the century, when the city treasury faced financial difficulties. I seek to identify the reasons for these debts, the most important of them being expenses incurred for the upkeep of the Russian army. The treasury was also burdened with providing for the soldiers of the Grand Duchy of Lithuania and the city garrison. The extent and nature of these expenses is analysed. The largest creditors are registered in the article, and expenses for debt administration and return are also analysed.