Flax ( Linum usitatissimum L.) is an oilseed crop and the only species of Linaceae family that is commercially important and widely cultivated as the sixth oilseed crop of the world. To study the genetic variation for agronomic traits and yield components in some F 3 families of flax, an experiment was conducted in 1393 at the Research Farm of Isfahan University of Technology. In this experiment, 50 families in F 3 generation were evaluated according to a randomized complete block design with two replications. The results showed that there were significant differences among the families for the characters of the number of base branches per plant, capsules per plant, number of seeds per capsule, grain weight, grain yield per plant and seed yield per unit area. The coefficient of genetic variation for most of the studied traits were slightly smaller or very close to the coefficient of phenotypic variatio indicating that most of the observed variation for these traits were due to the genetic factors, thus a relatively high broad-sense heritability was estimated for these traits. The highest and lowest coefficient of variation was observed for seed yield per unit area and days to flowering, respectively. The numbers of branches per plant, number of capsules per plant and grain weight were positively and significantly correlated with seed yield per plant, and seed yield per unit area showed significant and positive correlation with the number of branches per plant, seed weight and seed yield per plant. The results of the stepwise regression showed that two traits of capsules per plant and seed weight were the most important yield components of seed yield per plant and totally contributed in 52% of its variation. Also, according to the path analysis results, the number of capsules per plant had the most positive direct effect on seed yield per plant. These results showed that capsules per plant were the most important yield component in these families, and it can be used as a selection criterion to improve the seed yield. Cluster analysis based on the agronomic traits separated the families into 4 distinct groups, in which the groups of 2 and 4 had the highest mean of seed weight, capsules per plant, number of branches per plant, seed yield per plant and seed yield per unit area. Keywords : Flax, Yield components, Genetic variation, Heritability