Wine is a popular alcoholic beverage and phenolic compounds stand out among the various chemical compounds in wine with organoleptic, antioxidant and anti-inflammatory properties. The technological process of wine production affects the composition of their phenolic components, so innovative technologies that can influence the phenolic compounds in wine are of great importance in this competitive market. The maturation of wine in sea springs is a novel technological process that, in addition to adding an attractive appearance to the wine bottle, potentially influences the wine’s final chemical composition. Furthermore, bottles of wine aged in sea springs often reach higher market prices. Therefore, the aim of this thesis is to determine the antioxidant potential and phenolic composition of wine samples aged either in sea springs or traditional cellars. Thirty samples of Malvasia white wines were analyzed using spectrophotometric and mass spectrometry methods, of which fifteen samples were matured in traditional cellars and fifteen samples were matured in a Northern Adriatic sea spring. All wines were aged for over one year prior to analysis. Spectrophotometric analysis of antioxidant potential and total phenols and flavonoids in the wine samples was performed using the cation radical reduction and Folin-Ciocalteu methods, respectively. Using a LC-QQQ mass spectrometry method, phenols in the wine were analyzed by quantitative LC-MS/MS analysis, qualitative MS scan analysis and MALDI-TOF fingerprint. The results were analyzed with statistical tests to determine significance differences between the two maturation processes. The antioxidant potential and total phenol and flavonoid levels did not differ significantly between the two maturation processes. However, LC-MS/MS analysis showed that wines matured in the sea spring differ significantly from cellar-matured wines in the concentration of six flavonoid compounds, but the total sum of phenolic compounds did not differ significantly between the two groups. This is encouraging for future optimization of wine maturation techniques in sea springs. This thesis is the first to describe the process of wine maturation in a sea spring and to analyze and compare wine samples matured in sea springs and cellars.