Results of HC3N observations of 15 dense molecular cloud cores, associated with bright IRAS sources in the outer Galaxy, are reported. HC3N column densities and emission region sizes have been calculated. The J=10-9 line analysis have been performed, along with the J=12-11 and J=5-4 data in the framework of the microturbulent isothermal model. The logarithms of densities found for 4 objects lie in the range: 5.5-5.9 being ∼(0.5-1) orders of magnitude higher than mean densities. Possible models for these objects should incorporate inhomogeneous density structure.