By interpretation of the letters u, d, r, l, up, down as ''move up, (d
own, right, left)'' with the pen, ''lift'' and ''sink'' the pen of a p
lotter we can associate a picture with a word. The set of pictures ass
ociated with the words in a regular (context-free) string language is
called a regular (context-free) picture language or chain code picture
language. In this paper we discuss the decidability status of the fol
lowing problems for regular and context-free picture languages: Is som
e picture a subpicture of all pictures of the language? Does the langu
age contain a picture with a given property? Have all pictures of the
language a given property?