Pacemaker apnea scan algorithms are able to screen for sleep apnea. We investigated whether these systems were able to accurately detect sleep-disordered breathing (SDB) in two patients from an outpatient clinic. The first patient suffered from ischemic heart failure and severe central sleep apnea (CSA) and underwent adaptive servoventilation therapy (ASV). The second patient suffered from dilated cardiomyopathy and moderate obstructive sleep apnea (OSA). Pacemaker read-outs did not match polysomnography (PSG) recordings well and overestimated the apnea–hypopnea index. However, ASV therapy-induced SDB improvements were adequately recognized by the apnea scan of the Boston Scientific INVIVE® cardiac resynchronization therapy pacemaker. Detection of obstructive respiratory events using impedance-based technology may underestimate the number of events, as frustrane breathing efforts induce impedance changes without significant airflow. By contrast, in the second case, apnea scan overestimated the number of total events and of obstructive events, perhaps owing to a very sensitive but less specific hypopnea definition and detection within the diagnostic algorithm of the device. These two cases show that a pacemaker apnea scan is able to reflect SDB, but PSG precision is not met by far. The device scan revealed the decline of SDB through ASV therapy for CSA in one patient, but not for OSA in the second case. To achieve reliable monitoring of SDB, further technical developments and clinical studies are necessary.