The relationships between two types of blocking over the Asian continent (60E--140E) during northern winter are examined by using both the NCEP-NCAR and the ECMWF reanalysis data for the period 1958--2005. Both the Ω-type blocking occurring over the region of 60E--100E and the dipole-type blocking occurring over the region of 100E--140E contribute to a stronger than normal east Asian winter monsoon (EAWM). However, their blocking frequency shows rather different interannual variation. In addition, the dipole-type blocking frequency is negatively correlated with ENSO activity. While the blocking frequency of the Ω type is positively correlated with the snow cover during the preceding autumn over the Siberian High region and far eastern Russia, that of the dipole type is negatively correlated with the Eurasian snow cover. Thus, the combination of the variation in tropical SST and snow cover may exert a favorable influence on a relatively strong EAWM by the generation and maintenance of blocking patterns.