Photolysis of pyridine derivatives in the presence of SnBU4 or Sn2Bu6 leads to butyl derivatives in the alpha and gamma positions. With 2,4-dicyanopyridine ipso-substitution of the cyano groups with the butyl groups exclusively occurs. With 4-cyanopyridine both ipso-substitution and substitution at the 2-position take place. A photo-induced electron-transfer mechanism is suggested.