Abstract:The seasonal imbalances and price premiums of natural gas imports (NGIs) seriously affect the sustainability of these imports in major Northeast Asian countries, namely, China, Japan, and South Korea. Research on NGI seasonality might provide new insights that may help solve these issues. Unfortunately, little research has been conducted on this topic. Therefore, this paper examined the seasonalities of Chinese, Japanese, and South Korean NGIs using the X-12-ARIMA model to analyze monthly and quarterly data. The results suggest that Chinese NGIs lacks identifiable monthly or quarterly seasonality,