In the last decades, mortality from severe acute illnesses has considerably declined thanks to the advances in intensive care medicine. Meanwhile, critical care physicians realized that life-sustaining treatments (LST) may not be appropriate for every patient, and end-of-life care in the Intensive Care Unit (ICU) started to receive growing attention. Most deaths occurring in the ICU now follow a decision to forgo life-sustaining treatments (DFLST), which can be implemented either by withdrawing (WDLST) or withholding (WHLST) life-sustaining treatments. Despite the broad consensus about the equivalence of the two practices from an ethical point of view, the issue of the best option between WDLST and WHLST constantly gives rise to controversies in clinical practice. This review is not intended to take a stand for or against WDLST or WHLST. Based on available evidence, the definitions of the two practices are first presented. Secondly, the preferences of ICU physicians towards WDLST and WHLST are examined. Finally, some arguments are offered outlining pros and cons of WDLST and WHLST, stressing that the clinician's attention should focus on an early and thorough recognition of patients in need of a DFLST, rather than on the theoretical strength and weakness of the two practices. This approach will enable physicians to make informed decisions on how to implement the limitation of LSTs, considering the patients' clinical conditions and preferences, the circumstances and needs of their families.