Boil the potatoes in a large pot until tender. Let them cool slightly and then cut them into 3/4 inch dice.
Place the potatoes in a large bowl. Add the eggs, dill, scallions, and radishes.
In a small bowl, stir together the Greek yogurt, salt, and vinegar. Pour the dressing over the potato mixture and stir to coat evenly. The dressing will absorb well if the potatoes are still warm.