The role of metrology in the system of technical regulation and the scope of the federal law «On ensuring the uniformity of measurements» No. 102-FL in the forms of product conformity assessment forms, forms for confirming the compliance of measuring instruments with mandatory requirements and requirements performed on a voluntary basis are considered. The role of metrology is shown in the most important element of the technical regulation system – conformity assessment, due to the fact that in all its forms, proof of compliance with requirements is provided by objective methods, i.e. with the use of measuring instruments. At the same time, the measuring technique is a specific product, to which, besides technical, and in some cases first of all, metrological requirements are met, i.e. requirements for metrological characteristics of measuring instruments. The problems of unambiguous understanding and application of assessment forms and confirmation of compliance of measuring instruments with metrological and technical requirements, such as: verification, validation, calibration, introduced by international and national regulatory documents are discussed.