The article presents the author’s considerations on the significance of the investment package diversifying natural gas supplies as part of the Northern Gate in ensuring Poland’s energy security. Data found in literature concerning the possibilities of importing the raw material by sea (terminals, gas pipelines) includes investments at various stages of concept development and construction. However, these documents lack cohesive information about a full investment package being implemented. The author has thus attempted at creating variants concerning the diversification capacities of the Republic of Poland in reference to several key offshore and onshore projects. A problem has therefore been formulated: To what extend will the Northern Gate investment package increase Poland’s energy security as a result of increased supply of natural gas from the sea? To answer this questions, researchers were forced to verify their working hypothesis which assumed that Northern Gate investments including a comprehensive package of projects had the potential of significantly improving the level of energy security in Poland by extending the possibility of importing natural gas. To solve the problem and verify the hypothesis, the researchers applied systemic analysis, deduction and variant analysis, which were used to estimate the possible import capacities of the raw material by sea. As a result of the works, the researchers created four variants including various investment projects assuming the import of 7.75 m3 to 30,95 B m3 of natural gas a year by sea. The variant which was adopted as the most probable indicates the possibility of importing 17.75 through 22.75 B m3 of gas a year, which is 111% of the average annual demand in Poland.