The chapter has been divided by Mackay (2008) into four main parts:
PART 1: The Agony of Suffering (Lamentations 3:1–24)
The Darkness of Affliction (Lamentations 3:1–18)
The Dawning of a New Day (Lamentations 3:19–24)
PART 2: Moving Out Of Darkness (Lamentations 3:25–39)
The Lord's Goodness (Lamentations 3:25–27)
Living with Catastrophe (Lamentations 3:28–30)
The Lord's Compassion (Lamentations 3:31–33)
Divine Disapproval (Lamentations 3:34–36)
The Sovereignty of the Lord (Lamentations 3:37–39)
PART 3: Self-Examination and Complaint (Lamentations 3:40–48)
PART 4: Prayer Based on Past Experience (Lamentations 3:49–66).1
Another workable division (Huey, 1993):
An individual's description of the suffering (Lamentations 3:1–20)
God's past mercies as the basis for future hope (Lamentations 3:21–39)
An appeal for God's mercy (Lamentations 3:40–51)
An appeal for deliverance and a call for vengeance (Lamentations 3:52–66).2
1 I am the man who has seen affliction under the rod of his wrath;