The topic of this master’s thesis deals with conservation and restoration treatments conducted on the easel painting Woman in blue dress painted by an unknown painter, under the mentorship of professor Tamara Ukrainčik. The painting technique used in the making of this painting is oil on canvas and the dimensions are 66,5 x 53,5 cm. The painting is dated to the first half of the 19th century, and the style matches that of the biedermeier period. All necessary research, including both investigation into the stylistic and technological characteristics, was carried out in the hopes of getting a clearer picture of the object in advance of performing any conservation and restoration treatments. Thus, the thesis includes a detailed description of the time period from which the artwork originates, as well as the technique used for its construction and the causes of its demise. After concluding all necessary information, a detailed work plan was made and later adapted as necessary. All decisions regarding conservation and restoration treatments were made in subsequence to the performance of instrumental analysis. The fact that there were conservation and restoration treatments performed on the painting at least once in the past caused a big impact on the materials and methods chosen this time. Materials added in previous treatments would not be todays first choice, when we take into regard the contemporary approach to restoration. However, the results of those treatments are still mostly in good condition, and that's the reason we decided to keep some of them. In these treatments, it was necessary to adjust newly added materails to the old ones, while looking at it through the lens of a contemporary approach to the ethics of conservation-restoration work. All treatments have been thoroughly documented in written, graphic and photographic form. Graphic charts and any used analysis results are included as well.