I am having trouble with an application, using VB6 and ADO to access an
mdb file.

The table has 3 text fields with 255 chars length each, when I do a query
of the following form:

SELECT F1 & F2 & F3 FROM Table

The result is a recordset, but only the first 255 chars are returned.

Anybody knows the reason of this behaviour or can give me an idea
of what to do.

I am concatenating the fields since the result is being used by a Spread7
control.

It is because the String field can only take 255 characters. The 3 concatenated together make a string field. If you want them all use a memo field and then you will get the desired result.