The syndrome of the sinking skin flap (SSSF) has been described as one of the causes of neurological deficits after decompressive craniectomy We report a case of a 57-year-old woman with SSSF. Two years earlier, this patient, with no neurological deficits, underwent removal of the bone flap during treatment of an epidural abscess due to wound infection after a clipping operation for a ruptured aneurysm. The patient, who subsequently developed a sinking skin flap, gradually presented with gait disturbance and poor activity around one year before she came to our facility. On admission, neurological examination showed left hemiparesis and mild confusion. Cranioplasty with titanium mesh plate was performed. The cerebral blood flow value in CT perfusion imaging in the symptomatic hemisphere increased from 23 to 31 cc/100g/min, and the value in the contralateral side increased from 37 to 41 cc/100g/min after cranioplasty. CT perfusion imaging after cranioplasty revealed the improvement of cerebral blood flow not only on the symptomatic side but also on the contralateral side. The patient recovered well and was discharged without hemiparesis and confusion 2 weeks after cranioplasty. As far as we know, this is the first reported case of SSSF examined with CT perfusion imaging before and after cranioplasty.