In international large-scale surveys, constructed response (CR) items are increasingly being used and multiple-choice (MC) items are being used less frequently. In this article the two item types will be compared in terms of any differences they have on national mean scores. TIMSS 1995 and TIMSS 1999 data have been used. Are there different effects of the question types for mathematics and science? Does the introduction of open-ended items into the math and science tests affect the math and science achievement results?