Whether to die, or when to die?

Consider the following hypothetical cases:

• Smith, a 40 year old man, has a permanent condition which causes constant, unremitting pain, but which does not affect his life expectancy. In the absence of intervention, he can be expected to live another 35 years. Smith does not want to live out those remaining years, so his doctor provides him with a lethal drug, which Smith self-administers.
• Jones, a 40 year old man, presents to the Emergency Department with an advanced form of meningococcal meningitis. The condition has progressed too far for life-saving treatment: he will certainly die within 24 hours. Around a minute before death is imminent, he will enter a state of excruciating pain. Jones does not want to live through this last minute. He requests a lethal drug which his doctor provides and he will administer when the pain begins.

Is there an important difference between these cases? Practical Ethics