In view of these feasibility and efficacy results, we attempted cryoablation in the reported two patients who have previously undergone pneumonectomies. In these two patients, we experienced no apparent complications, the decrease in respiratory function was minimal, and the local control was also considered to be satisfactory. Recently, results of radiofrequency ablation in single-lung patients after pneumonectomies have been reported with good feasibility.9 Although the radiofrequency procedures were done under general anesthesia, as opposed to local anesthesia for cryoablation, the data support the concept that needle ablation procedures, including cryoablation, may be safely applicable in single-lung patients. In terms of safety, there is a statement from the US Food and Drug Administration that discourages the use of radiofrequency ablation in lung tumors because of reports of serious complications, but it is difficult to find definitive support for this statement in the published literature. In fact, the majority of reports indicate that radiofrequency ablation for lung tumors is safe.10 In terms of efficacy, there is evidence to suggest that cryoablation may result in improved local control in renal tumors,11 but, to our knowledge, there are no studies comparing the two modalities in lung tumors. Hence, we consider that a retrospective study comparing the two modalities is a minimum requirement to evaluate any comparative strengths or weaknesses of each of the procedures in terms of safety and efficacy. Animal experiments comparing the differential effects of the two modalities on the lung tissue may also be necessary.