Quercus robur dieback remained not completely explained even though numerous papers have been focused on this problem. In the future, more severe and unpredictable climate conditions are expected which may additionally accelerate oaks dieback. It is essential to understand the relationship between climate and tree growth to make proper management measures. Declining and vital group of pedunculate oaks from two sites in Slovenia were compared. Comparing to the group of vital trees, group of declining trees showed superior growth in earlier stage of development which may contribute to their higher vulnerability to environmental changes. Dieback of declining trees was at first visible in ring width (RW) and latewood width (LW). Only in 1995, when final stage of mortality started, smaller conductive elements were observed. Relationship between climate and analyzed parameters (ring width, earlywood width, latewood width, total vessel area, mean vessel area and maximal vessel area) was related to site specifications and was therefore considerable different for both groups. Vital trees from slightly hilly location were responding to the mean temperatures and sum of precipitations. Declining group from lowlands in Cigonca was corresponding only to the mean monthly temperatures.