Strong earthquakes, occurred in the last five decades of the 20th century, have provoked severe damage to masonry structures (including historical constructions and monuments). Post-earthquake repair and strengthening has followed the advancing knowledge in the field of existing masonry constructions, and the formulation of respective guidelines. Due to the insufficient knowledge on the behavior of historical masonry typologies (especially, the vulnerable multi-leaf masonries) and on the seismic behavior of masonry structures in general, methodologies and techniques adequate for RC structures were often adopted. Subsequent earthquakes, occurred in the last twenty years, have offered evidence allowing for previous interventions to be assessed. This paper presents selected cases of successful and unsuccessful (pre- or post-earthquake) intervention schemes, along with interpretation of their effect on the seismic behavior of the respective historical constructions. Conclusions are drawn, confirming the validity of recent national and international guidelines requiring exhaustive documentation of the existing structure, selection of adequate materials ensuring physical-chemical compatibility with the in-situ ones, and, hence, durability of interventions, etc.