Radiated emission propagates through the air, conducted one – via the wires or via any other conductor (such as metal parts of equipment). You can’t have one without the other – any voltage or current generates fields, and any field generates voltages and currents in conductors – after all, this how antennas work. The dealing with these two types of emission is quite different.
Radiated emission is greatly reduced with the distance from the source – for the curious of us, it follows inverse square law. Double the distance from the source and the field drops four times. Practically, if interference is your concern, it means that you only need to worry about radiated sources located close to where it matters for you.
Conducted emission also diminishes with the distance, but to a much smaller degree – it simply doesn’t spread around as the fields do. Higher frequencies diminish much faster due to parasitic capacitance and inductance in wires. Realistically, only signals under 1MHz matter – the rest are greatly attenuated, even if the original signal has higher bandwidth http://www.onfilter.com