Research results of mnemonic abilities of 7-12 years children with developmental delays are presented. Research aim was experimental investigation of productivity and qualitative identity of mnemonic abilities of younger students with developmental delays. The method of development of mnemonic activity by V.D. Shadrikov, L.V. Cheremoshkina and the technique of mnemonic abilities diagnosis developed on its basis by L.V. Cheremoshkina were used for the study of mnemonic abilities. Research consisted of several stages: pilot study, experimental research (the test task - memorizing of a card #1; the basic task - memorizing of cards #2 and #3; reproduction of cards #2 и #3; poll of students), mathematical data processing, classification and description of levels of mnemonic abilities development of younger students with developmental delays. Revealed, that the structure of the mnemonic abilities of 7-12 years children with developmental delays differs by underdevelopment of operational mechanisms. Memory functions are based on use of inborn mechanisms. There are children who differ by certain underdevelopment of perceptive abilities and attentional abilities. Operational mechanisms of mnemonic abilities of 7-12 years students with developmental delays are at early stages of the formation. At the analysis of results the effect of inability to copy a simple nonverbal material after its correct reproduction by subjects is revealed. Assumptions of its possible reasons are discussed. This effect needs the further explanation in terms of psychology of abilities, neuropsychology, and neurophysiology.