The purpose of the paper is to show the size and the basic characteristics of customs compliance costs of importers (legal entities and small business) in the Republic of Croatia in 2001. The customs compliance costs comprise those costs that the customs payers incur in order to meet the provisions of the customs laws and the requests of the customs administration. Only the amount of the customs duty paid and any distortion costs arising from paying customs duty are not customs compliance costs. The research was carried out by the face-to-face interview method, in the period from June to October 2002. It was concluded that the Croatian customs compliance costs in 2001 were regressive. It was also concluded that costs were large in comparison with the total customs revenue and GDP. It is estimated that customs compliance costs for importers (legal entities and small businesses) in RC in 2001 were around 1,006 million HRK. That is 0.6% GNP and around 31% of total Croatian customs revenues in 2001. There is not, unfortunately, a single foreign research of the costs of customs compliance that could be used as a comparison. What is more the research faced many problems (e,g. non-representative and small samples) so one should be cautious when using its results. For this reason we would conclude that the primary purpose of this research is to pose relevant questions related to the conceptual and methodological problems of customs compliance cost research. Furthermore it should indicate possible size and characteristics of the customs compliance costs in the RC.