At ECOOP 2010 in Maribor, Slovenia, the two workshops MASPEGHI (MechAnisms for SPEcialization, Generalization and inHerItance) and ICOOOLPS (Implementation, Compilation, Optimization of Object-Oriented Languages, Programs and Systems) were combined because both were rather small and shared common concerns, their topic areas being strongly related. Six papers had been accepted to MASPEGHI, but only five were presented because the authors of one paper could not attend the conference and workshop. Three papers had been accepted to ICOOOLPS, and all were also presented. The workshop authors were later asked to submit extended versions of their papers for possible publication in this special section. We received two extended papers from ICOOOLPS and one from MASPEGHI. They were carefully reviewed by three reviewers each, and then revised by the authors according to the reviewers' comments. In our opinion, all revised papers were interesting, of high quality and significantly extended from the workshop versions. One of them, however, needed more work from its authors, and they could not complete it within a reasonable time. As a consequence, only two extended, reviewed and revised papers are now published in this special section.