BACKGROUND: Small cell lung cancer (SCLC) is acknowledged as the most aggressive histological subtype among the various types of lung cancer. Among patients with advanced-stage SCLC, liver metastasis (LM) is frequently observed and is associated with the most unfavorable prognosis. The purpose of the present study is to investigate the synchronous metastatic sites in SCLC patients with LM, and to construct a nomogram for predicting the survival of these patients. METHODS: The data of SCLC patients with LM in the Surveillance, Epidemiology, and End Results (SEER) database were retrospectively analyzed. Univariate and multivariate Cox analyses were conducted to identify independent prognostic factors. A prognostic nomogram was developed and validated through calibration curves, receiver operating characteristic (ROC) curves, and decision curve analysis (DCA). There were 128 patients from the Jilin Cancer Hospital selected for external validation. The overall survival (OS) of patients with LM was estimated using the Kaplan-Meier method, and survival differences were compared using the log-rank test. RESULTS: This study included a total of 8,858 patients, with independent prognostic factors for LM in SCLC patients being age, gender, primary site, surgery, radiotherapy, chemotherapy, brain metastasis, and lung metastasis. The calibration, ROC curves, and DCA collectively demonstrated the outstanding predictive accuracy of the prognostic nomogram. Bone was the most common accompanying organ for metastasis in SCLC-LM patients, followed by the lungs. Among the eight different groups based on metastatic patterns, compared to patients with isolated LM, those with concurrent metastases at other sites had a higher risk of death and poorer prognosis. Patients with LM accompanied by lung metastasis had the poorest prognosis, with a median survival time of 2 months. CONCLUSIONS: The nomogram is anticipated to serve as a precise and individualized instrument for forecasting the survival of SCLC with LM. Identifying the locations of synchronous extra LM and their corresponding prognoses can aid in guiding treatment decisions and optimizing treatment approaches.