An apparatus for inspecting containers includes a rotation device which is adapted to rotate the container about the axis of symmetry; a camera sensitive to said predetermined electromagnetic radiation and with the container located in the field of view thereof; a processing unit to control the rotation device to move the container at a first angular speed constant for a first time period; acquiring at least a first and a second series of images of a portion of the container in a rotation thereof through 360°; to identify defective areas having at least one characteristic different from the characteristics of adjacent areas, generating first and second maps of the defective areas; to compare the position of the defective areas of the maps; to establish that first impurities are present in the container or in the liquid contained in the container.