The present invention relates to tetrahydrophthalimides of formula I wherein the variables are defined according to the description, processes and intermediates for preparing the benzoxazinones of the formula I, compositions comprising them and their use as herbicides, i.e. for controlling harmful plants, and also a method for controlling unwanted vegetation which comprises allowing a herbicidal effective amount of at least one tetrahydrophthalimide of the formula I to act on plants, their seed and/or their habitat.