Colorado potato beetle (Leptinotarsa decemlineata Say 1824) is the most important pest of mercantile potato that has been successfully overtaken by using insecticides of various mechanisms of action for years. However, over time, there has been an increasing number of cases of proven resistance to insecticides that have been in use for many years. Therefore, it was necessary to check the status of resistance to these insecticides as well as the efficacy of some new ones registered for this purpose. The aim of the study was to determine the efficacy of seven insecticides registered for the control of Colorado potato beetle in the Republic of Croatia. The efficacy of the recommended dose, half dose and 1/5 of the recommended dose were determined. Colorado potato beetles were collected at seven localities of the potato growing area and the experiments were conducted using the method of soaking the leaves into a sprayer (IRAC No. 7). In total, 21 insecticide variants were tested in the study. The results found low efficacy of chlorpyrifos and cypermethrin and unchanged resistance status compared to data from 30 years ago. At all localities, high resistance of Colorado potato beetles to lufenuron and metaflumizone, insecticides that have been recommended as an alternative to classic insecticides, has been identified. Spinosad and thiacloprid have been found to have satisfactory efficacy at half of the sites investigated and can therefore still be used in protection programs with regular monitoring of resistance status (thiacloprid until expiry of the marketing authorization). Regular monitoring of the efficacy of the insecticides used in the control of Colorado potato beetle is required, because, according to the results of this study, resistance is expected to increase, as well as to explore new alternative (and non-chemical) methods of controlling Colorado potato beetles.