Fibrolamellar hepatocellular carcinoma (fHCC) was diagnosed in three young patients aged 17, 22 and 24 years by magnetic resonance imaging and biopsy. All patients had normal results of standard biochemical tests but elevated levels of procalcitonin (PCT) and C-reactive protein (CRP) in the absence of infection – PCT levels were 41, 5.8 and 1.2 ng/ml (normal range < 0.05 ng/ml). After surgery (right hepatectomy), CRP levels normalized in all patients and PCT normalized in the last two patients. In the first patient, the PCT decreased to 0.07 ng/ml at three months, but increased to 0.8 ng/ml after the appearance of bone metastases at the seventh month. After further treatment, including resection and immunotherapy (bevacizumab and atezolizumab), PCT returned to 0.04 ng/ml with no evidence of recurrence at 42 months. The other two patients showed normal PCT levels and no evidence of recurrence 16 and 6 months after treatment. The authors recommend measuring PCT levels at least once during the examination of patients with fHCC, as this analysis is commonly available and may be useful in monitoring the disease.