Are there look-alikes?
Good heavens, yes. But also, no. There are dozens of species and varieties of impatiens. But if you know what to look for (see 'What does it look like?), the differences are fairly obvious. The impatiens most likely to be confused with policeman’s helmet is Himalayan balsam (Impatiens balfourii; left side of photo), itself a species of concern. I. balfourii tends to have a longer, straighter spur than I. glandulifera, shorter plants (three feet tall or less), and two-toned, white and purple/pink flowers.