The paper considers the peculiarities of deflagration-to-detonation transition (DDT) in obstructed channels filled with gaseous mixtures. The necessary stage in flame evolution prior to DDT is the stage of flame propagation in so-called "chocked flame" regime. The structure of the chocked flame is studied numerically in details that allows formulating the criterion of its stability. In turn, the stability of chocked flame determines the possibility of further flame acceleration and subsequent DDT. Such a criterion is of purely chemical nature and can be estimated using the parametric study involving simple one-dimensional calculations. It should be however noted that to get the prediction of DDT in real complex geometry one should additionally estimate the particular conditions of chocked flame formation in the given geometry. Moreover, the particular mechanisms of detonation onset should be analyzed. Such a complex analysis involving both chemical criterion and analysis of geometrical conditions is applied to the estimation of DDT possibility in obstructed channels. The obtained results are in a good agreement with available experimental data.