Generally, impatiens tend to get leggy if:

• Spaced too close in the flower bed (closer than 10")
• Given high levels of phosphorus/ammoniumcal nitrogen. Fertilizing sparingly is recommended.
• Grown under very low light conditions
• Given abundant moisture.

Typcially it is a combination. Impatiens grown under high moisture and fertilizer conditions but in low light will grow tall. If you plant in fair amount of sun, they require more water and fertilizer, than plants grown in heavy shade. Soil which stays consistently damp also creates very tall lush plants but with few flowers.

Luckily, the solution is very easy. Sheer it down to the ground and wait 3-4 weeks for a new flush growth. Adjust fertilizer and watering practices as needed.

Weird plants. Some years they are great and other years they will be weak in exactly the same spot. I suspect periodic pest problems might hit the plants in some years. Or maybe its just the weather.

I want to post a photo of my impatiens, which are the leggy type, but with no blooms at all this year. How do I put the photos on here? Thanks for any help.
Bonnie in Southeast Ok

If you want consistently great impatiens, I suggest you ammend your soil with compost. Impatiens LOVE compost! My impatiens are almost thigh high and blooming profusely as of today -- August 9, and I planted them in April.

kdjoergensen has got it right, but I would add that you should take the parts you cut off and stick them in the ground as cuttings. Or, put them in a hanging basket to grow and LET them get leggy (pretty!) or share them with a friend.