[en] To determine whether sirolimus has beneficial effects on lymphangioleiomyomatosis (LAM) lung cysts in CT with long-term follow-up (FU) and to investigate whether CT is an appropriate imaging biomarker to monitor and evaluate LAM progression. In this retrospective study, 73 female patients diagnosed with definite LAM between May 2001 and June 2018 were included. Among these, 39 (53.4%) were treated with sirolimus. Quantitative and qualitative CT scoring for lung cysts (CS) were performed and compared between time points (baseline vs. FU at starting sirolimus, baseline vs. last FU, and FU at starting sirolimus vs. last FU for patients treated with sirolimus; baseline vs. last FU for patients without sirolimus). The correlation between CS at each time point and pulmonary function tests (PFTs) at each time point in the patients treated with sirolimus was also investigated. The quantitative and qualitative analyses and PFT results were compared between time points. In both quantitative and qualitative analyses, CS significantly increased from baseline to FU after starting sirolimus, and from baseline to last FU (all p < 0.05), whereas there was no significant difference between scores at the start of sirolimus vs. last in the patients treated with sirolimus. After sirolimus treatment, diffusing capacity for carbon monoxide (DL${}_{CO}$) was significantly increased. There were significant correlations between CS at each time point and PFT (correlation coefficient [r], − 0.383–0.935; all p < 0.001). Patients with LAM benefited from sirolimus. CT could be a useful imaging biomarker for evaluating and monitoring lung cysts in LAM.